Accuracy tests for simulations of VAV dual-duct, single-zone, four-pipe fan-coil, and four-pipe induction air-handling systems.ABSTRACT This paper provides a method for verifying ver·i·fy tr.v. ver·i·fied, ver·i·fy·ing, ver·i·fies 1. To prove the truth of by presentation of evidence or testimony; substantiate. 2. the accuracy of computer models that simulate simulate - simulation the performance of the air-handling components of four types of heating, ventilating ventilating Natural or mechanically induced movement of fresh air into or through an enclosed space. The hazards of poor ventilation were not clearly understood until the early 20th century. Expired air may be laden with odors, heat, gases, or dust. , and air-conditioning air-conditioning Control of temperature, humidity, purity, and motion of air in an enclosed space, independent of outside conditions. In a self-contained air-conditioning unit, air is heated in a boiler unit or cooled by being blown across a refrigerant-filled coil and then systems: the dual-fan VAV dual-duct system, the single-zone system, the four-pipe fan-coil system, and the four-pipe induction induction, in electricity and magnetism induction, in electricity and magnetism, common name for three distinct phenomena. Electromagnetic induction system. To accomplish this, a detailed description of each system and its operating parameters was developed and a set of eight test conditions was generated, consisting of carefully chosen space loads and weather conditions. Each of the systems was simulated at each of the defined conditions. The thermodynamic properties Here is a partial list of thermodynamic properties of fluids:
2. in the total coil loads was 1.8%, and the average of the absolute deviations In statistics, the absolute deviation of an element of a data set is the absolute difference between that element and a given point. Typically the point from which the deviation is measured is the value of either the median or the mean of the data set. was 0.4%. These validated val·i·date tr.v. val·i·dat·ed, val·i·dat·ing, val·i·dates 1. To declare or make legally valid. 2. To mark with an indication of official sanction. 3. results can be used by program developers or users to test the performance of the air-side simulations contained in most building energy analysis computer programs. INTRODUCTION It is difficult for the user of a building energy analysis (BEA BEA - Basic programming Environment for interactive-graphical Applications, from Siemens-Nixdorf. ) computer program to know that the program is providing accurate answers. BEA programs are complex and carry out a large number of calculations. They also use empirical em·pir·i·cal adj. 1. Relying on or derived from observation or experiment. 2. Verifiable or provable by means of observation or experiment. 3. models to simulate many building components. Even a long and detailed hand calculation would check only one program path. One part of a BEA program is easier to check than the others. This is the simulation The mathematical representation of the interaction of real-world objects. See scientific application and simulator. Simulation A broad collection of methods used to study and analyze the behavior and performance of actual or theoretical systems. of the air side of the air-handling system. Most of the analysis of the air side of the air-handling system involves only fundamental equations such as the first law of thermodynamics first law of thermodynamics law dealing with the transformation of energy. States that energy can neither be created nor destroyed, only converted from one form to another. and the continuity equation. Also, most BEA programs do not take into account transients when simulating air-handling systems. Therefore, it is possible to perform a simple manual analysis to verify (1) To prove the correctness of data. (2) In data entry operations, to compare the keystrokes of a second operator with the data entered by the first operator to ensure that the data were typed in accurately. See validate. a BEA program's simulation of an operating condition for an air-handling system. By repeating this analysis for several different systems and for several different sets of load and weather conditions, a set of test conditions can be generated that will make it possible to validate To prove something to be sound or logical. Also to certify conformance to a standard. Contrast with "verify," which means to prove something to be correct. For example, data entry validity checking determines whether the data make sense (numbers fall within a range, numeric data the fundamental elements of a BEA program that simulates the air-handling system. The objective of the work reported here was to generate such a set of data, to enable the user to test the accuracy of the simulation of air-handling systems by a building energy analysis computer program. The data presented here have been produced by analysis of the performance of four different types of air-handling systems (the dual-fan VAV dual-duct system, the single-zone system, the four-pipe fan-coil system, and the four-pipe induction system) for six different sets of outdoor and room conditions, using spreadsheets The following is a list of spreadsheets. Freeware/open source software Online spreadsheets
All deviations were checked by hand by a third analyst and the results reconciled rec·on·cile v. rec·on·ciled, rec·on·cil·ing, rec·on·ciles v.tr. 1. To reestablish a close relationship between. 2. To settle or resolve. 3. . These results are reported in detail in the RP-865 final report to ASHRAE (Yuill and Haberl 2002). Because of the extensive validation See validate. validation - The stage in the software life-cycle at the end of the development process where software is evaluated to ensure that it complies with the requirements. checks that were carried out, any deviation of the results of a building energy analysis computer program from the results presented here should be suspected to be an error or an approximation approximation /ap·prox·i·ma·tion/ (ah-prok?si-ma´shun) 1. the act or process of bringing into proximity or apposition. 2. a numerical value of limited accuracy. in the program that is being tested. In spite of in opposition to all efforts of; in defiance or contempt of; notwithstanding. See also: Spite the effort that was expended ex·pend tr.v. ex·pend·ed, ex·pend·ing, ex·pends 1. To lay out; spend: expending tax revenues on government operations. See Synonyms at spend. 2. to validate the set of results presented here, it is possible that not every case was analyzed an·a·lyze tr.v. an·a·lyzed, an·a·lyz·ing, an·a·lyz·es 1. To examine methodically by separating into parts and studying their interrelations. 2. Chemistry To make a chemical analysis of. 3. correctly. Therefore, the thermodynamic properties (dry-bulb temperature The dry-bulb temperature is the temperature of air measured by a thermometer freely exposed to the air but shielded from radiation and moisture. In construction, it is an important consideration when designing a building for a certain climate. , humidity humidity, moisture content of the atmosphere, a primary element of climate. Humidity measurements include absolute humidity, the mass of water vapor per unit volume of natural air; relative humidity (usually meant when the term humidity ratio, specific volume, and enthalpy enthalpy (ĕn`thălpē), measure of the heat content of a chemical or physical system; it is a quantity derived from the heat and work relations studied in thermodynamics. ) and the mass flow rate are listed for each point of interest along the airflow path through the air-handling system. These data are presented in the RP-865 final report to ASHRAE (Yuill and Haberl 2002). Using these data, a user who finds a deviation between the program being checked and the present results can easily check the calculations by hand and establish whether an error has occurred in the validation data. The methodology described in this paper was used to develop a set of test cases for three other types of systems. However, space limitations did not permit the presentation of all of the results in a single paper. A previous companion paper (Yuill et al. 2005) provided similar test cases for a constant volume terminal reheat Re`heat´ v. t. 1. To heat again. 2. To revive; to cheer; to cherish. Verb 1. reheat - heat again; "Please reheat the food from last night" system, a variable air volume system, and a single-fan constant volume dual-duct system. The next section of this report contains a brief description of each of the systems analyzed and a schematic A graphical representation of a system. It often refers to electronic circuits on a printed circuit board or in an integrated circuit (chip). See logic gate and HDL. diagram diagram /di·a·gram/ (di´ah-gram) a graphic representation, in simplest form, of an object or concept, made up of lines and lacking pictorial elements. of each system. Following that is a description of the six test cases to which the systems were subjected. A table summarizing and comparing the coil loads predicted by the two independent analyses of each system is contained in the next section. SYSTEM DESCRIPTIONS General Features Figures 1, 2, 3, and 4 schematically sche·mat·ic adj. Of, relating to, or in the form of a scheme or diagram. n. A structural or procedural diagram, especially of an electrical or mechanical system. show the systems described here. These are: the dual-fan VAV dual-duct system (VAVDD), the single-zone system (SZ), the four-pipe fan-coil system (FC), and the four-pipe induction system (IU). All of these systems are analyzed without economizers (that is, with a constant minimum outdoor air supply), and the first two systems (VAVDD and SZ) are analyzed with return air temperature economizers and with return air enthalpy economizers. As the diagrams show, each of the systems provides heating and cooling to one or two rooms. The heating or cooling loads in those rooms, as well as the temperatures to be maintained, are specified spec·i·fy tr.v. spec·i·fied, spec·i·fy·ing, spec·i·fies 1. To state explicitly or in detail: specified the amount needed. 2. To include in a specification. 3. in Tables 1A (I-P I-P Intermediate Pressure units) and 1B (SI units (Système International d'Unites) A system of standard units of measurement finalized at the 14th General Conference on Weights and Measures in 1971. It is based on seven units of measure, including three from the MKS system (meter-kilogram-second), the ampere for ) for each test case. The system descriptions are based on the systems described by Knebel (1983), Haberl et al. (2002), and in the documentation for the DOE 2.1 (Winkelman et al. 1993) and BLAST (BSL (language) BSL - A variant of IBM's PL/S systems language. Versions: BSL1, BSL2. 1999) building energy analysis computer programs. Economizer e·con·o·mize v. e·con·o·mized, e·con·o·miz·ing, e·con·o·miz·es v.intr. 1. To practice economy, as by avoiding waste or reducing expenditures. 2. Operations Return Air Temperature Economizer (RATE). The return air temperature economizer operates as follows. When the outdoor air temperature is higher than the return air temperature, the air-mixing system will provide the minimum outdoor air required to minimize In a graphical environment, to hide an application that is currently displayed on screen. For example, in Windows and Mac, the application's window is removed from the screen and represented by an icon on the Windows Taskbar. In the Mac, the icon is placed in the Dock. See Win Minimize windows. the cooling coil load. When the outdoor air temperature is between the return air temperature and the final coil leaving temperature, the recirculation Noun 1. recirculation - circulation again circulation - the spread or transmission of something (as news or money) to a wider group or area damper damp·er n. 1. One that deadens, restrains, or depresses: Rain put a damper on our picnic plans. 2. An adjustable plate, as in the flue of a furnace or stove, for controlling the draft. will close and the relief and outdoor air dampers will open wide. The supply air will be 100% outdoor air. This mode of operation is known as the economizer mode. When the outdoor air temperature drops below the required coil leaving temperature, the recirculation damper opens again and is modulated mod·u·late v. mod·u·lat·ed, mod·u·lat·ing, mod·u·lates v.tr. 1. To adjust or adapt to a certain proportion; regulate or temper. 2. with the relief and outdoor air dampers to mix the recirculating and outdoor air to the required coil leaving temperature. This mode of operation is known as the free cooling mode. When the outdoor air is very cold, it may not be possible to mix outdoor and bypass In communications, to avoid the local telephone company by using satellites and microwave systems. air to achieve the desired coil leaving temperature without reducing the outdoor airflow rate below the minimum allowed. The minimum amount of outdoor air required will be provided in this case, and the mixed-air temperature will fall below the desired coil leaving temperature. Return Air Enthalpy Economizer (RAEE). The return air enthalpy economizer operates similarly to the return air temperature economizer. The two economizer systems differ only in determining the outdoor condition at which the switch from 100% outdoor air to minimum outdoor air is to be made. The "return air enthalpy economizer" mode of operation makes this switch as the enthalpy of the outdoor air rises from just below to just above the return air enthalpy. No Economizer (NE). When no economizer is used, the outdoor air dampers are set to supply a fixed amount of outdoor air. The remainder of the supply air is drawn through the recirculation dampers. Operation of Fans and Coils Unlike most of the components of an air-handling system, fans and coils cannot be modeled simply by applying fundamental principles of conservation of mass in energy. The simulation of the performance of a cooling coil will usually be based on an empirical model that uses experimental data collected by testing the coil. However, the limiting case of cooling coil performance is a cooling coil that delivers saturated saturated /sat·u·rat·ed/ (sach´ah-rat?ed) 1. denoting a chemical compound that has only single bonds and no double or triple bonds between atoms. 2. unable to hold in solution any more of a given substance. air at the coil leaving temperature. By assuming that the coil operates in this manner, it is possible to develop a standard model for the operation of the entire air-handling system. This model will not test the simulation of the cooling coil, but it permits simulation of the remainder of the air-handling system to be tested. The same argument applies to the simulation of the fans. The following assumptions were made concerning fan and coil operation in both systems. For the fans, it is assumed that fan pressure rise varies with the square of the volumetric volumetric /vol·u·met·ric/ (vol?u-met´rik) pertaining to or accompanied by measurement in volumes. vol·u·met·ric adj. Of or relating to measurement by volume. airflow rate through the fan. The pressure rise across the supply fan is 2 in. [H.sub.2]O (498.16 Pa) at 1300 cfm (613.5 L/s), and the pressure rise across the return fan is 1 in. [H.sub.2]O (249.08 Pa) at 800 cfm (377.6 L/s). Each fan operates at a constant 70% efficiency, and all fan energy is transferred to the air that is being moved. The fan motor energy loss is not transferred to the moving air (i.e., the fan motor is assumed to be outside of the air-handling unit). All fan volume flow rate calculations use the specific volume of air entering the fan. In all cases, exhaust Exhaust may refer to: In mathematics:
[FIGURE 1 OMITTED] [FIGURE 2 OMITTED] [FIGURE 3 OMITTED] [FIGURE 4 OMITTED] The operation of cooling coils in both systems is as follows. Cooling coils are assumed to operate with a bypass factor of zero. This means that if the cooling coil leaving temperature is less than the dew-point Dew´-point` n. 1. (Meteor.) The temperature at which dew begins to form. It varies with the humidity and temperature of the atmosphere. temperature of the air entering the cooling coil, the air will leave the coil at 100% relative humidity relative humidity n. The ratio of the amount of water vapor in the air at a specific temperature to the maximum amount that the air could hold at that temperature, expressed as a percentage. . If the cooling coil leaving temperature is greater than the dew-point of the air entering the cooling coil, no condensation will occur. The cooling coil maintains its setpoint Setpoint may refer to:
tr.v. pre·heat·ed, pre·heat·ing, pre·heats To heat (an oven, for example) beforehand. pre·heat  er n. coil is set
to 10[degrees]F below the supply air setpoint temperature. Therefore,
when the outdoor air temperature is so low that the air-mixing system
cannot produce air at the desired mixed-air temperature, the supply air
temperature will fall below 55[degrees]F (12.78[degrees]C). When it
reaches 45[degrees]F (7.22[degrees]C), the preheat coil will begin to
operate. Like the cooling coil, the preheat coil has no throttling range
and maintains its setpoint temperature precisely.
In the systems that have zone coils, these coils modulate to meet the room loads, delivering air to each room at whatever temperature is necessary to maintain the thermostat thermostat, automatic device that regulates temperature in an enclosed area by controlling heating or refrigerating systems. It is commonly connected to one of these systems, turning it on or off in order to maintain a predetermined temperature. setpoint precisely, without a throttling range. Dual-Fan VAV Dual-Duct System (VAVDD) A schematic diagram of this system is shown in Figure 1. The air-mixing system operates as described in the discussion about economizers. The preheat coil remains off unless the mixed-air temperature drops below the setpoint, which is 45[degrees]F (7.22[degrees]C) in the cases presented. If the mixed-air temperature drops below this setpoint, the preheat coil will modulate to maintain the coil leaving air temperature at this setpoint without a throttling range. Each of the two variable-volume supply fans has the design airflow rate specified as 1300 cfm (613.5 L/s). In this system, a portion of the supply air is delivered through the cold deck A stacked deck is a deck of playing cards arranged in a preset order, designed to give a specific outcome when the cards are dealt. A cold deck is a stacked deck which is typically switched with the deck actually being used in the game in question, to the benefit of . If the air temperature after the preheat coil is such that the temperature after the cold supply fan remains at or under the cold deck setpoint temperature (55[degrees]F [12.78[degrees]C] in the cases presented) without additional cooling, the cooling coil remains off. Otherwise, the cooling coil modulates to maintain the cold deck setpoint temperature after the cold deck supply fan. The cold deck supply fan modulates to provide the proper amount of supply air. A portion of the supply air also flows through the hot deck (1) The part of a magnetic tape unit that holds and moves the tape reels. The term may refer to any equipment that serves as a physical framework for electronic or mechanical devices. See rack. See also DEC. . If the air temperature after the preheat coil is such that the temperature after the hot deck supply fan remains at or above the hot deck setpoint temperature (110[degrees]F [43.33[degrees]C] in the cases presented) without additional heating, the heating coil remains off. Otherwise, the heating coil modulates to maintain the hot deck setpoint temperature after the hot deck supply fan. The hot deck supply fan modulates to provide the proper amount of supply air. Zone mixing dampers and VAV dampers are controlled by thermostats in the zones to maintain the zone setpoint temperature with no throttling range or dead band. At design cooling load conditions, the VAV damper will be fully open and the mixing damper will stop all flow from the hot deck and allow the full volume of supply air to come from the cold deck. As the cooling load in a room drops below the design value, the VAV damper will close until the minimum mass flow rate (corresponding to the mass exhausted from the space) is reached. If the cooling load drops below this point, the mixing damper will modulate, allowing more supply air to come from the hot deck and less from the cold deck. As the cooling load drops to zero and the heating load begins to increase, the mixing damper will eventually allow all supply air to come from the hot deck. If the heating load continues to rise beyond this point, the VAV damper will open more. This will allow more hot deck air to enter the room to maintain the zone temperature setpoint. They system shown in Figure 1 can also be configured con·fig·ure tr.v. con·fig·ured, con·fig·ur·ing, con·fig·ures To design, arrange, set up, or shape with a view to specific applications or uses: to operate as a single-fan dual-duct VAV system (Haberl et al. 2002). Single-Zone Air Conditioner conditioner, n 1. an additive substance used to increase the effectiveness of another substance. 2. a substance added to enamel that improves a sealant's ability to adhere. (SZ) A schematic diagram of this system is shown in Figure 2. A similar system serves each zone. The air-mixing system operates as described above. The supply fan provides the specified constant volume of supply air. In difference to the VAVDD system, the supply air setpoint changes as the load in the space changes. If the air-mixing system is able to keep the air temperature after the supply fan at this setpoint, the heating coil and cooling coil remain off. These coils supply heating or cooling as needed as needed prn. See prn order. to maintain the supply air setpoint if the air-mixing system is not able to keep the air temperature after the supply fan at the supply air setpoint. Four-Pipe Fan-Coil System (FC) A schematic diagram of this system is shown in Figure 3. A similar system serves each zone. A fixed amount of utdoor air is introduced to each zone at a mass flow rate sufficient to replace the exhaust air. A supply fan provides the specified constant volume of supply air from the fan-coil unit in each zone. The heating and cooling coils supply heating or cooling as needed to maintain the room temperature at its setpoint. (Note that the pressure rise and the efficiency of the fans in the fan-coil units are not realistic. The same values that were used for the central systems were used here to simplify the task of those who use this document to validate the operation of building energy analysis computer programs.) Four-Pipe Induction System (IU) A schematic diagram of this system is shown in Figure 4. Outdoor air is introduced to the primary air handler
An air handler, or air handling unit and often abbreviated to AHU at a mass flow rate sufficient to replace the exhaust air removed from the zone. The preheat coil remains off unless the outdoor air temperature drops below the setpoint, which is 45[degrees]F (7.22[degrees]C) in the cases presented. If the outdoor air temperature drops below this setpoint, the preheat coil will modulate to maintain the coil leaving air temperature at this setpoint. If the temperature after the preheat coil is such that the temperature after the fan will remain at or under the primary supply air setpoint temperature (55[degrees]F [12.78[degrees]C] in the cases presented) without additional cooling, the cooling coil remains off. Otherwise, the cooling coil modulates to maintain the primary supply air setpoint temperature after the supply fan. Primary air is introduced into each zone's induction unit, where a secondary flow of zone supply air is induced induced /in·duced/ (in-dldbomacst´) 1. produced artificially. 2. produced by induction. induced, adj artificially caused to occur. induced induction. . The total volume of supply air for each zone is constant. The setpoint for the mixed supply air for each zone changes as the space load changes. The heating and cooling coils supply heating or cooling as needed to maintain the zone setpoint temperature. The heating and cooling coils are assumed to be in the stream of induced air returning from the room. The conditioned air is then mixed with the induction air. The specified supply airflow rate is at the specific volume of the mixed air entering the room from the induction unit. Test Cases Each of the mechanical systems was tested over a range of six conditions using all possible economizer cycles (for VAVDD and SZ). The six conditions are summarized in Table 1. Other fixed conditions and their applicability to the various systems are noted in Table 2. Test Case Definitions The sensible sensible /sen·si·ble/ (sen´si-b'l) 1. capable of sensation. 2. perceptible to the senses. sen·si·ble adj. 1. Perceptible by the senses or by the mind. load for each zone was defined in this analysis as the amount of energy required to cool or heat a room's supply air from supply air temperature to room air temperature. The negative sensible loads shown in Table 1 are heating loads and the positive sensible loads are cooling loads. The latent Hidden; concealed; that which does not appear upon the face of an item. For example, a latent defect in the title to a parcel of real property is one that is not discoverable by an inspection of the title made with ordinary care. load for each zone was defined in this analysis as the amount of energy required to vaporize va·por·ize v. To convert or be converted into a vapor. Vaporize To dissolve solid material or convert it into smoke or gas. the water added to the zone at 0[degrees]F (-17.78[degrees]C) plus the energy required to heat that added vapor vapor /va·por/ (va´por) pl. vapo´res, vapors [L.] 1. steam, gas, or exhalation. 2. an atmospheric dispersion of a substance that in its normal state is liquid or solid. from 0[degrees]F (-17.78[degrees]C) to room temperature. Supply Airflow Rate. The supply volume flow rate for each zone is measured at the supply fan inlet inlet /in·let/ (-let) a means or route of entrance. pelvic inlet the upper limit of the pelvic cavity. thoracic inlet the elliptical opening at the summit of the thorax. . As the temperature and humidity preceding the supply fan change, the specific volume of that air changes. This means that the mass flow rate of supply air will change slightly from case to case. Exhaust Airflow Rate. The exhaust volume flow rate for each zone is measured at the inlet of that zone's exhaust fan. As the temperature and humidity preceding an exhaust fan change, the specific volume of that air changes. This means that the mass flow rate of exhaust air from each zone will change slightly from case to case. RESULTS OF THE ANALYSIS Thermodynamic properties and mass flow rates were calculated for each of the operating points in each of the heating and cooling systems cooling systems for housed animals include spraying of roofs with water, evaporative pads with fans, foggers and misters; for pastured animals shelter from the sun by trees or artificial shade devices and cooling ponds are used. operating at the conditions specified above. The property values tabulated are dry-bulb temperature, humidity ratio, specific volume, and enthalpy of the moist moist having a moderate moisture content, slightly wet to the touch. moist dermatitis see moist dermatitis of rabbits. moist grain storage grain stored at about 30% moisture in airtight silos. air. The mass flow rate at each point is also presented. These data are tabulated in the final project report to ASHRAE (Yuill et al. 2002). Tables 3 through 9 contain the coil loads calculated for each simulated combination of the six cases, two mechanical systems, and three economizer types. In each table, the values obtained for the cooling loads by Penn State University (PSU PSU - power supply unit ) and by Texas A & M University (TAMU TAMU Texas A&M University TAMU Texas Agricultural and Mechanical University TAMU Tyler Area Macintosh Users (Tyler, Texas) TAMU Tropical Aviation Meteorological Unit ) are shown. The deviations between the two sets of total coil loads calculated are less than 1% in 18 of the 22 nonzero non·ze·ro adj. Not equal to zero. nonzero Not equal to zero. cases analyzed and less than 2% in the other four cases. The average of the absolute deviations was 0.4%. Three main problems were encountered in getting this agreement. First, many deviations were caused by minor data entry or programming errors. Second, early in the project, there were also some deviations due to misinterpretations of the system description or test case parameters. These two types of error were eliminated as the deviations they caused were noted. The other cause of deviations was the approach to calculating air density. One author calculated the changes in air density with temperature and relative humidity. The other assumed constant density at standard conditions. This caused deviations of a few percent. Therefore, the first approach (variable density) was adopted, and many of the deviations in coil loads were eliminated. Those using these results may encounter the same problem because many building energy analysis programs also assume constant density throughout the air side calculation. USING THE RESULTS To test the air-handling system simulation section of a BEA computer program, the user must apply the program to the analysis of the four systems that are described in this paper. The zone sensible and latent loads, temperatures, and other conditions must be set to the values described here. The coil loads predicted by the BEA program being tested can then be compared with the values tabulated below. If there is close agreement in every case, that segment of the BEA program that simulates the air-handling system is working properly for the particular systems tested. If there is disagreement, the user should first check the input data that were supplied to the BEA program. The pattern of disagreement will usually pinpoint any input data problems. If the input data appear correct, then any disagreement in load prediction "Prediction is very difficult, especially if it's about the future." - Niels Bohr A prediction is a statement or claim that a particular event will occur in the future in more certain terms than a forecast. may indicate a problem in the algorithms The following is a list of the algorithms described in Wikipedia. See also the list of data structures, list of algorithm general topics and list of terms relating to algorithms and data structures. of the BEA program. If the user of this procedure is attempting to develop confidence in the results of a BEA program that was developed by others, then the procedure should be repeated until a program is found that agrees well with the coil loads listed in this paper. On the other hand, if the user is a developer of a BEA program, it will be necessary to find the source of the problem. In that case the RP-865 final report to ASHRAE (Yuill and Haberl 2002) should be obtained. That report contains tables of thermodynamic properties and mass flows for all points in the air-handling system. The program developer can produce a similar table for the program under development, and a comparison of the two will usually highlight any error that may have occurred in the program under development. CONCLUSIONS The heating and cooling coil loads tabulated here provide the BEA program user and the program developer with a method of checking the performance of that segment of a BEA program that simulates air-side systems. By comparing the output of the program with the data presented in this paper, potential errors in a BEA program can quickly be identified. A companion paper provides similar accuracy tests for constant volume, dual-duct and variable volume air-handling systems. ACKNOWLEDGMENTS See About this product. The work described here was supported by ASHRAE Research Project RP-865. REFERENCES ASHRAE. 1993. 1993 ASHRAE Handbook--Fundamentals. Atlanta Atlanta (ətlăn`tə, ăt–), city (1990 pop. 394,017), state capital and seat of Fulton co., NW Ga., on the Chattahoochee R. and Peachtree Creek, near the Appalachian foothills; inc. 1847. : American American, river, 30 mi (48 km) long, rising in N central Calif. in the Sierra Nevada and flowing SW into the Sacramento River at Sacramento. The discovery of gold at Sutter's Mill (see Sutter, John Augustus) along the river in 1848 led to the California gold rush of Society of Heating, Refrigerating re·frig·er·ate tr.v. re·frig·er·at·ed, re·frig·er·at·ing, re·frig·er·ates 1. To cool or chill (a substance). 2. To preserve (food) by chilling. and Air-Conditioning Engineers, Inc. ASHRAE. 1995. 1995 ASHRAE Handbook--HVAC Applications. Atlanta: American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. BSL. 1999. BLAST 3.0 Users Manual. Urbana-Champaign, IL: Building Systems Laboratory, Department of Mechanical and Industrial Engineering, University of Illlinois. Haberl, J., N. Saman, and T. Bou-Saada. 2002. Air-side energy use calculations for seven HVAC (Heating Ventilation Air Conditioning) In the home or small office with a handful of computers, HVAC is more for human comfort than the machines. In large datacenters, a humidity-free room with a steady, cool temperature is essential for the trouble-free systems: Dual duct constant volume (DDCAV), dual duct variable volume (DDVAV), constant volume with reheat (CAVRH); variable volume with reheat (VAVRH), four pipe fan coil Unit (FC), four pipe induction unit (FI), and single zone (SZ) systems. Energy Systems Laboratory Report, ESL-TR-01/02-02, Texas A & M University, College Station, Texas College Station is a city in Brazos County, Texas, situated in Central Texas. It is located in the heart of the Brazos Valley. The city is located within the most populated region of Texas, near to three of the 10 largest cities in the United States - Houston, Dallas, and San . Knebel, D.E. 1983. Simplified sim·pli·fy tr.v. sim·pli·fied, sim·pli·fy·ing, sim·pli·fies To make simple or simpler, as: a. To reduce in complexity or extent. b. To reduce to fundamental parts. c. energy analysis using the modified mod·i·fy v. mod·i·fied, mod·i·fy·ing, mod·i·fies v.tr. 1. To change in form or character; alter. 2. bin method. ASHRAE. Winkelman, F.C., B.E. Birdsall, W.F. Buhl, K.L. Ellington, A.E. Erdem, J.J. Hirsch Hirsch (deer in German and Yiddish) may refer to:
Yuill, G.K., and J.S. Haberl. 2002. Development of accuracy tests for mechanical system simulation, Final report (RP-865). American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc., Atlanta. Yuill, G.K., J.S. Haberl, and J.S. Caldwell Caldwell, city (1990 pop. 18,400), seat of Canyon co., SW Idaho, on the Boise River; inc. 1890. On the site of an Oregon Trail camping ground, the city is a major processing and distribution center for an agricultural and livestock area. . 2005. Accuracy tests for simulations of constant volume, dual duct, and variable volume air-handling systems. ASHRAE Transactions 111(2). G.K. Yuill, PhD, PEng Fellow ASHRAE J.S. Haberl, PhD, PE Member ASHRAE J.S. Caldwell Associate Member ASHRAE G.K. Yuill is director of the Architectural Engineering Architectural engineering A discipline that deals with the technological aspects of buildings, including the properties and behavior of building materials and components, foundation design, structural analysis and design, environmental system analysis and Program at the University of Nebraska Nebraska (nəbrăs`kə), Great Plains state of the central United States. It is bordered by Iowa and Missouri, across the Missouri R. (E), Kansas (S), Colorado (SW), Wyoming (NW), and South Dakota (N). , Lincoln Lincoln, city and district, England Lincoln, city (1991 pop. 79,980) and district, Lincolnshire, E England, in the Parts of Kesteven, on the Witham River. . J.S. Haberl is an associate professor of architecture at Texas A & M University, College Station, Texas. J.S. Caldwell is an associate principal at James Posey James Mikely Mantell Posey, Jr. (born January 13 1977 in Cleveland, Ohio) is an American professional basketball player, currently playing small forward for the Boston Celtics of the National Basketball Association. Associates, Baltimore, Maryland "Baltimore" redirects here. For the surrounding county, see Baltimore County, Maryland. For other uses, see Baltimore (disambiguation). Baltimore is an independent city located in the state of Maryland in the United States. .
Table 1a. Test Cases (I-P Units)
Case 1 Case 2 Case 3 Case 4 Case 5 Case 6
Ambient
Dry bulb ([degrees]F) -20 30 60 80 77 74
Wet bulb ([degrees]F) -20 20 45 75 55 70
Zone 1
Setpoint temperature 70 71 74 75 74 74
([degrees]F)
Sensible cooling -10,000 -2,000 5,000 10,000 5,000 5,000
load (Btu/h)
Latent cooling 2,000 2,000 2,000 2,000 2,000 2,000
load (Btu/h)
Zone 2
Dry-bulb setpoint 72 73 76 77 76 76
temperature
([degrees]F)
Sensible cooling -8,000 1,000 8,000 12,000 8,000 8,000
load (Btu/h)
Latent cooling 3,000 3,000 3,000 3,000 3,000 3,000
load (Btu/h)
Table 1b. Test Cases (SI Units)
Case 1 Case 2 Case 3 Case 4 Case 5 Case 6
Ambient
Dry bulb -28.89 -1.11 15.56 26.67 25.00 23.33
([degrees]C)
Wet bulb -28.89 -6.67 7.22 23.89 12.78 21.11
([degrees]C)
Zone 1
Dry-bulb setpoint 21.11 21.67 23.33 23.89 23.33 23.33
temperature
([degrees]C)
Sensible cooling -2.931 -0.5862 1.4655 2.931 1.4655 1.4655
load (kW)
Latent cooling 0.5862 0.5862 0.5862 0.5862 0.5862 0.5862
load (kW)
Zone 2
Dry-bulb setpoint 22.22 22.78 24.44 25.00 24.44 24.44
temperature
([degrees]C)
Sensible cooling -2.3448 0.2931 2.3448 3.5172 2.3448 2.3448
load (kW)
Latent cooling 0.8793 0.8793 0.8793 0.8793 0.8793 0.8793
load (kW)
Table 2. Test Case Parameters
Variable-Volume
Dual-Duct Single-Zone
2 in. (498.16 Pa) design X X
supply fan pressure
1 in. (249.08 Pa) design X X
return fan pressure
55[degrees]F (12.78[degrees]C)
supply air setpoint
55[degrees]F (12.78[degrees]C) X
cold deck setpoint
110[degrees]F (43.33[degrees]C) X
hot deck setpoint
1[degrees]F (0.56[degrees]C) X X
return duct heat gain
600 cfm (283.17 L/s) zone 1 supply X
200 cfm (94.39 L/s) zone 1 exhaust X X
700 cfm (330.37 L/s) zone 2 supply X
300 cfm (141.59 L/s) zone 2 exhaust X X
Return air temperature economizer X X
Return air enthalpy economizer X X
45[degrees]F (7.22[degrees]C) X
preheat coil setpoint
Four-Pipe Four-Pipe
Fan-Coil Induction
2 in. (498.16 Pa) design X X
supply fan pressure
1 in. (249.08 Pa) design
return fan pressure
55[degrees]F (12.78[degrees]C) X
supply air setpoint
55[degrees]F (12.78[degrees]C)
cold deck setpoint
110[degrees]F (43.33[degrees]C)
hot deck setpoint
1[degrees]F (0.56[degrees]C)
return duct heat gain
600 cfm (283.17 L/s) zone 1 supply X X
200 cfm (94.39 L/s) zone 1 exhaust X X
700 cfm (330.37 L/s) zone 2 supply X X
300 cfm (141.59 L/s) zone 2 exhaust X X
Return air temperature economizer
Return air enthalpy economizer
45[degrees]F (7.22[degrees]C) X
preheat coil setpoint
Table 3a. Coil Loads Summary--Case 1: All Air-Mixing Systems (I-P Units)
System Zone 1 Zone 2
Btu/h Heating Cooling Heating Cooling Heating
VAV Dual-Duct
PSU 66,816 0
TAMU 66,851
Difference -35 0 0 0 0
% Diff. -0.05 0.00 0.00 0.00 0.00
Fan-Coil
PSU 28,660 0 36,573
TAMU 28,665 36,767
Difference 0 0 -5 0 -14.12
% Diff. 0.00 0.00 -0.02 0.00 -0.04
Induction
PSU 34,855 0 15,179 0 16,382
TAMU 34,885 15,162 16,357
Difference -30 0 17 0 25
% Diff. -0.09 0.00 0.11 0.00 0.15
Single-Zone
PSU 28,457 0 36,543
TAMU 28,444 36,544
Difference 0 0 13.34 0 -0.89
% Diff. 0.00 0.00 0.05 0.00 0.00
Maximum Difference
Maximum % Difference
Zone 2 Total
Btu/h Cooling Heating Cooling
VAV Dual-Duct
PSU 66,816 0
TAMU 66,851 0
Difference 0 -35 0
% Diff. 0.00 -0.05 0.00
Fan-Coil
PSU 0 65,413 0
TAMU 65,433 0
Difference 0 -19.57 0
% Diff. 0.00 -0.03 0.00
Induction
PSU 0 66,416 0
TAMU 66,404 0
Difference 0 12 0
% Diff. 0.00 0.02 0.00
Single-Zone
PSU 0 65,000 0
TAMU 64,988 0
Difference 0 12.45 0
% Diff. 0.00 0.02 0.00
Maximum Difference 35 0
Maximum % Difference 0.05 0
Table 3b. Coil Loads Summary--Case 1: All Air-Mixing Systems (SI Units)
System Zone 1 Zone 2
kJ/h Heating Cooling Heating Cooling Heating
VAV Dual-Duct
PSU 70,495 0 0 0 0
TAMU 70,532 0 0 0 0
Difference -37 0 0 0 0
% Diff. -0.05 0.00 0.00 0.00 0.00
Fan-Coil
PSU 0 0 30,238 0 38,776
TAMU 0 0 30,244 0 38,791
Difference 0 0 -6 0 -15
% Diff. 0.00 0.00 -0.02 0.00 -0.04
Induction
PSU 36,774 0 16,015 0 17,284
TAMU 36,806 0 15,997 0 17,258
Difference -31 0 17 0 26
% Diff. -0.09 0.00 0.11 0.00 0.15
Single-Zone
PSU 0 0 30,024 0 38,555
TAMU 0 0 30,010 0 38,556
Difference 0 0 14 0 -1
% Diff. 0.00 0.00 0.05 0.00 0.00
Maximum Difference
Maximum % Difference
Zone 2 Total
kJ/h Cooling Heating Cooling
VAV Dual-Duct
PSU 0 70,495 0
TAMU 0 70,532 0
Difference 0 -37 0
% Diff. 0.00 -0.05 0.00
Fan-Coil
PSU 0 69,014 0
TAMU 0 69,035 0
Difference 0 -21 0
% Diff. 0.00 -0.03 0.00
Induction
PSU 0 70,073 0
TAMU 0 70,060 0
Difference 0 12 0
% Diff. 0.00 0.02 0.00
Single-Zone
PSU 0 68,579 0
TAMU 0 68,565 0
Difference 0 13 0
% Diff. 0.00 0.02 0.00
Maximum Difference 37 0
Maximum % Difference 0.05 0
Table 4a. Coil Loads Summary--Case 2: All Air-Mixing Systems (I-P Units)
System Zone 1 Zone 2
Btu/h Heating Cooling Heating Cooling Heating
VAV Dual-Duct
PSU 23,563 0
TAMU 23,579
Difference -16 0 0 0 0
% Diff. -0.07 0.00 0.00 0.00 0.00
Fan-Coil
PSU 10,109 0 11,984
TAMU 10,116 12,000
Difference 0 0 -7 0 -16
% Diff. 0.00 0.00 -0.07 0.00 -0.13
Induction
PSU 8,028 0 7,384 0 7,687
TAMU 8,035 7,367 7,662
Difference -7 0 17 0 25
% Diff. -0.09 0.00 0.23 0.00 0.33
Single-Zone
PSU 9,882 0 11,748
TAMU 9,887 11,768
Difference 0 0 -4 0 -20
% Diff. 0.00 0.00 -0.04 0.00 -0.17
Maximum Difference
Maximum % Difference
Zone 2 Total
Btu/h Cooling Heating Cooling
VAV Dual-Duct
PSU 23,563 0
TAMU 23,579
Difference 0 -16 0
% Diff. 0.00 -0.07 0.00
Fan-Coil
PSU 0 22,093 0
TAMU 22,116
Difference 0 -23 0
% Diff. 0.00 -0.10 0.00
Induction
PSU 0 23,099 0
TAMU 23,064
Difference 0 35 0
% Diff. 0.00 0.15 0.00
Single-Zone
PSU 0 21,630 0
TAMU 21,655
Difference 0 -25 0
% Diff. 0.00 -0.11 0.00
Maximum Difference 35 0
Maximum % Difference 0.15 0.00
Table 4b. Coil Loads Summary--Case 2: All Air-Mixing Systems (SI Units)
System Zone 1 Zone 2
kJ/h Heating Cooling Heating Cooling Heating
VAV Dual-Duct
PSU 24,860 0 0 0 0
TAMU 24,877 0 0 0 0
Difference -17 0 0 0 0
% Diff. -0.07 0.00 0.00 0.00 0.00
Fan-Coil
PSU 0 0 10,666 0 12,644
TAMU 0 0 10,673 0 12,661
Difference 0 0 -7 0 -17
% Diff. 0.00 0.00 -0.07 0.00 -0.13
Induction
PSU 8,470 0 7,791 0 8,110
TAMU 8,477 0 7,773 0 8,084
Difference -8 0 18 0 26
% Diff. -0.09 0.00 0.23 0.00 0.33
Single-Zone
PSU 0 0 10,427 0 12,395
TAMU 0 0 10,431 0 12,416
Difference 0 0 -5 0 -21
% Diff. 0.00 0.00 -0.04 0.00 -0.17
Maximum Difference
Maximum % Difference
Zone 2 Total
kJ/h Cooling Heating Cooling
VAV Dual-Duct
PSU 0 24,860 0
TAMU 0 24,877 0
Difference 0 -17 0
% Diff. 0.00 -0.07 0.00
Fan-Coil
PSU 0 23,310 0
TAMU 0 23,334 0
Difference 0 -24 0
% Diff. 0.00 -0.10 0.00
Induction
PSU 0 24,371 0
TAMU 0 24,334 0
Difference 0 37 0
% Diff. 0.00 0.15 0.00
Single-Zone
PSU 0 22,821 0
TAMU 0 22,847 0
Difference 0 -26 0
% Diff. 0.00 -0.11 0.00
Maximum Difference 37 0
Maximum % Difference 0.15 0.00
Table 5a. Coil Loads Summary--Case 3: No Economizer (I-P Units)
System Zone 1 Zone 2
Btu/h Heating Cooling Heating Cooling Heating
VAV Dual-Duct
PSU 0 5,039
TAMU 5,042
Difference 0 -3 0 0 0
% Diff. 0.00 -0.06 0.00 0.00 0.00
Fan-Coil
PSU 0 2,699 0
TAMU 2,686
Difference 0 0 0 12.86 0
% Diff. 0.00 0.00 0.00 0.48 0.00
Induction
PSU 0 3,166 0 943 0
TAMU 3,207 939
Difference 0 -41 0 4 0
% Diff. 0.00 -1.30 0.00 0.42 0.00
Single-Zone
PSU 0 2,947 0
TAMU 0 2,923 0
Difference 0 0 0 24 0
% Diff. 0.00 0.00 0.00 0.83 0.00
Maximum Difference
Maximum % difference
Zone 2 Total
Btu/h Cooling Heating Cooling
VAV Dual-Duct
PSU 0 5,039
TAMU 0 5,042
Difference 0 0 -3
% Diff. 0.00 0.00 -0.06
Fan-Coil
PSU 3,698 0 6,397
TAMU 3,676 0 6,362
Difference 22.4 0 35.26
% Diff. 0.61 0.00 0.55
Induction
PSU 1,300 0 5,409
TAMU 1,293 0 5,439
Difference 7 0 -30
% Diff. 0.54 0.00 -0.55
Single-Zone
PSU 3,957 0 6,904
TAMU 3,916 0 6,839
Difference 41 0 65
% Diff. 1.03 0.00 0.95
Maximum Difference 0 65
Maximum % difference 0 0.95
Table 5b. Coil Loads Summary--Case 3: No Economizer (SI Units)
System Zone 1 Zone 2
kJ/h Heating Cooling Heating Cooling Heating
VAV Dual-Duct
PSU 0 5,316 0 0 0
TAMU 0 5,320 0 0 0
Difference 0 -3 0 0 0
% Diff. 0.00 -0.06 0.00 0.00 0.00
Fan-Coil
PSU 0 0 0 2,848 0
TAMU 0 0 0 2,834 0
Difference 0 0 0 14 0
% Diff. 0.00 0.00 0.00 0.48 0.00
Induction
PSU 0 3,340 0 995 0
TAMU 0 3,384 0 991 0
Difference 0 -43 0 4 0
% Diff. 0.00 -1.30 0.00 0.42 0.00
Single-Zone
PSU 0 0 0 3,109 0
TAMU 0 0 0 3,084 0
Difference 0 0 0 26 0
% Diff. 0.00 0.00 0.00 0.83 0.00
Maximum Difference
Maximum % Difference
Zone 2 Total
kJ/h Cooling Heating Cooling
VAV Dual-Duct
PSU 0 0 5,316
TAMU 0 0 5,320
Difference 0 0 -3
% Diff. 0.00 0.00 -0.06
Fan-Coil
PSU 3,902 0 6,749
TAMU 3,878 0 6,712
Difference 24 0 37
% Diff. 0.61 0.00 0.55
Induction
PSU 1,372 0 5,707
TAMU 1,364 0 5,738
Difference 7 0 -32
% Diff. 0.54 0.00 -0.55
Single-Zone
PSU 4,175 0 7,284
TAMU 4,132 0 7,215
Difference 43 0 69
% Diff. 1.03 0.00 0.95
Maximum Difference 0 69
Maximum % Difference 0 0.95
Table 6a. Coil Loads Summary--Case 3: Economizers (I-P Units)
System Zone 1 Zone 2
Btu/h Heating Cooling Heating Cooling Heating
VAV Dual-Duct
PSU 0 3,353
TAMU 3,362
Difference 0 -9 0 0 0
% Diff. 0.00 -0.27 0.00 0.00 0.00
Single-Zone
PSU 0 0 0
TAMU 0 0 0 0 0
Difference 0 0 0 0 0
% Diff. 0.00 0.00 0.00 0.00 0.00
Maximum Difference
Maximum % Difference
Zone 2 Total
Btu/h Cooling Heating Cooling
VAV Dual-Duct
PSU 0 3,353
TAMU 0 3,362
Difference 0 0 -9
% Diff. 0.00 0.00 -0.27
Single-Zone
PSU 0 0 0
TAMU 0 0 0
Difference 0 0 0
% Diff. 0.00 0.00 0.00
Maximum Difference 0 9
Maximum % Difference 0 0.27
Table 6b. Coil Loads Summary--Case 3: Economizers (SI Units)
System Zone 1 Zone 2
kJ/h Heating Cooling Heating Cooling Heating
VAV Dual-Duct
PSU 0 3,538 0 0 0
TAMU 0 3,547 0 0 0
Difference 0 -9 0 0 0
% Diff. 0.00 -0.27 0.00 0.00 0.00
Single-Zone
PSU 0 0 0 0 0
TAMU 0 0 0 0 0
Difference 0 0 0 0 0
% Diff. 0.00 0.00 0.00 0.00 0.00
Maximum Difference
Maximum % Difference
Zone 2 Total
kJ/h Cooling Heating Cooling
VAV Dual-Duct
PSU 0 0 3,538
TAMU 0 0 3,547
Difference 0 0 -9
% Diff. 0.00 0.00 -0.27
Single-Zone
PSU 0 0 0
TAMU 0 0 0
Difference 0 0 0
% Diff. 0.00 0.00 0.00
Maximum Difference 0 9
Maximum % Difference 0 0.27
Table 7a. Coil Loads Summary--Case 4: All Air-Mixing Systems (I-P Units)
System Zone 1 Zone 2
Btu/h Heating Cooling Heating Cooling Heating
VAV Dual-Duct
PSU 0 47003
TAMU 46,892
Difference 0 111 0 0 0
% Diff. 0.00 0.24 0.00 0.00 0.00
Fan-Coil
PSU 0 19,853 0
TAMU 0 19,520 0
Difference 0 0 0 332 0
% Diff. 0.00 0.00 0.00 1.68 0.00
Induction
PSU 0 34,184 0 5,732 0
TAMU 33,134 5,723
Difference 0 113 0 9 0
% Diff. 0.00 0.33 0.00 0.16 0.00
Single-Zone
PSU 0 19,866 0
TAMU 19,629
Difference 0 0 0 237 0
% Diff. 0.00 0.00 0.00 1.19 0.00
Maximum Difference
Maximum % Difference
Zone 2 Total
Btu/h Cooling Heating Cooling
VAV Dual-Duct
PSU 0 47003
TAMU 0 46,892
Difference 0 0 111
% Diff. 0.00 0.00 0.24
Fan-Coil
PSU 24,701 0 44,554
TAMU 24,232 0 43,752
Difference 469 0 802
% Diff. 1.90 0.00 1.80
Induction
PSU 4,984 0 44,900
TAMU 4,973 0 43,830
Difference 11 0 133
% Diff. 0.22 0.00 0.30
Single-Zone
PSU 24,627 0 44,493
TAMU 24,337 0 43,966
Difference 290 0 527
% Diff. 1.18 0.00 1.18
Maximum Difference 0 802
Maximum % Difference 0 1.80
Table 7b. Coil Loads Summary--Case 4: All Air-Mixing Systems (SI Units)
System Zone 1 Zone 2
kJ/h Heating Cooling Heating Cooling Heating
VAV Dual-Duct
PSU - 49,591 - - -
TAMU - 49,474 - - -
Difference - 117 - - -
% Diff. 0.00 0.24 0.00 0.00 0.00
Fan-Coil
PSU - - - 20,946 -
TAMU - - - 20,595 -
Difference - - - 351 -
% Diff. 0.00 0.00 0.00 1.68 0.00
Induction
PSU - 36,066 - 6,048 -
TAMU - 34,958 - 6,038 -
Difference - 119 - 9 -
% Diff. 0.00 .33 0.00 0.16 0.00
Single-Zone
PSU - - - 20,960 -
TAMU - - - 20,710 -
Difference - - - 250 -
% Diff. 0.00 0.00 0.00 1.19 0.00
Maximum Difference
Maximum % Difference
Zone 2 Total
kJ/h Cooling Heating Cooling
VAV Dual-Duct
PSU - - 49,591
TAMU - - 49,474
Difference - - 117
% Diff. 0.00 0.00 0.24
Fan-Coil
PSU 26,061 - 47,007
TAMU 25,566 - 46,161
Difference 495 - 846
% Diff. 1.90 0.00 1.80
Induction
PSU 5,258 - 47,372
TAMU 5,247 - 46,243
Difference 12 - 140
% Diff. 0.22 0.00 0.30
Single-Zone
PSU 25,983 - 46,943
TAMU 25,677 - 46,387
Difference 306 - 556
% Diff. 1.18 0.00 1.18
Maximum Difference 0 846
Maximum % Difference 0 1.80
Table 8a. Coil Loads Summary--Case 5: Enthalpy Economizer (I-P Units)
System Zone 1 Zone 2
Btu/h Heating Cooling Heating Cooling Heating
VAV Dual-Duct
PSU 0 14,303
TAMU 14,312
Difference 0 -9 0 0 0
% Diff. 0.00 -0.06 0.00 0.00 0.00
Single-Zone
PSU 0 7,521 0
TAMU 7,649
Difference 0 0 0 -127 0
% Diff. 0.00 0.00 0.00 -1.70 0.00
Maximum Difference
Maximum % Difference
Zone 2 Total
Btu/h Cooling Heating Cooling
VAV Dual-Duct
PSU 0 14,303
TAMU 0 14,312
Difference 0 0 -9
% Diff. 0.00 0.00 -0.06
Single-Zone
PSU 9,436 0 16,957
TAMU 9,549 0 17,198
Difference -113 0 -241
% Diff. -1.20 0.00 -1.42
Maximum Difference 0 241
Maximum % Difference 0 1.42
Table 8b. Coil Loads Summary--Case 5: Enthalpy Economizer (SI Units)
System Zone 1 Zone 2
kJ/h Heating Cooling Heating Cooling Heating
VAV Dual-Duct
PSU - 15,090 - - -
TAMU - 15,100 - - -
Difference 0 -9 0 0 0
% Diff. 0.00 -0.06 0.00 0.00 0.00
Single-Zone
PSU - - - 7,935 -
TAMU - - - 8,070 -
Difference 0 0 0 -135 0
% Diff. 0.00 0.00 0.00 -1.70 0.00
Maximum Difference
Maximum % Difference
Zone 2 Total
kJ/h Cooling Heating Cooling
VAV Dual-Duct
PSU - - 15,090
TAMU - - 15,100
Difference 0 0 -9
% Diff. 0.00 0.00 -0.06
Single-Zone
PSU 9,956 - 17,891
TAMU 10,075 - 18,145
Difference -120 0 -254
% Diff. -1.20 0.00 -1.42
Maximum Difference 0 254
Maximum % Difference 0 1.42
Table 9a. Coil Loads Summary--Case 6: Enthalpy Economizer (I-P Units)
System Zone 1 Zone 2
Btu/h Heating Cooling Heating Cooling Heating
VAV Dual-Duct
PSU 0 26,687
TAMU 26,541
Difference 0 146 0 0 0
% Diff. 0.00 0.55 0.00 0.00 0.00
Single-Zone
PSU 0 8,596 0
TAMU 8,497
Difference 0 0 0 99 0
% Diff. 0.00 0.00 0.00 6.55 0.00
Maximum Difference
Maximum % Difference
Zone 2 Total
Btu/h Cooling Heating Cooling
VAV Dual-Duct
PSU 0 26,687
TAMU 0 26,541
Difference 0 0 146
% Diff. 0.00 0.00 0.55
Single-Zone
PSU 12,672 0 21,268
TAMU 12,484 0 20,981
Difference 188 0 287
% Diff. 1.48 0.00 1.35
Maximum Difference 0 287
Maximum % Difference 0 1.35
Table 9b. Coil Loads Summary--Case 6: Enthalpy Economizer (SI Units)
System Zone 1 Zone 2
kJ/h Heating Cooling Heating Cooling Heating
VAV Dual-Duct
PSU - 28,156 - - -
TAMU - 28,002 - - -
Difference 0 154 0 0 0
% Diff. 0.00 0.55 0.00 0.00 0.00
Single-Zone
PSU - - - 9,069 -
TAMU - - - 8,965 -
Difference - - - 104 -
% Diff. 0.00 0.00 0.00 1.15 0.00
Maximum Difference
Maximum % Difference
Zone 2 Total
kJ/h Cooling Heating Cooling
VAV Dual-Duct
PSU - - 28,156
TAMU - - 28,002
Difference 0 0 154
% Diff. 0.00 0.00 0.55
Single-Zone
PSU 13,370 - 22,439
TAMU 13,171 - 22,136
Difference 198 - 303
% Diff. 1.48 0.00 1.35
Maximum Difference 0 303
Maximum % Difference 0 1.35
TERMINOLOGY FOR FIGURES
VAVDD SZ FC IU
[A] X X X X Control system actuator
[C] X X X X Control system controller
[S] X X X X Control system sensor
[RH, IUHC] Reheat coil, induction unit
heating coil
[VAV] X VAV terminal box
[PHC] X Preheat coil
[HC] X X X X Heating coil
[CC, IUCC] X X X X Cooling coil, induction unit
cooling coil
ZSAW1,ZSAW2,ZSAW X X X X Zone #1 or Zone #2 supply air
humidity ratio (lb/lb, g/kg)
ZSADB1,ZSADB2, X X X X Zone #1 or Zone #2 dry-bulb
ZSADB temperature ([degrees]F,
[degrees]C)
ZSABP1,ZSABP2, X X X X Zone #1 or Zone #2 barometric
ZSABP pressure (psi, kPa)
QZS1,QZS2,QZS X X X X Zone #1 or Zone #2 sensible
heating or cooling (Btu/h, kW)
QZL1,QZL2,QZL X X X X Zone #1 or Zone #2 latent
heating or cooling (Btu/h, kW)
ZW1,ZW2,ZW X X X X Zone #1 or Zone #2 humidity
ratio (lb/lb, g/kg)
ZDB1,ZDB2,ZDB X X X X Zone #1 or Zone #2 dry-bulb
temperature ([degrees]F,
[degrees]C)
ZBP1,ZBP2,ZBP X X X Zone #1 or Zone #2 barometric
pressure (psi, kPa)
CFMZMIN1,CFMZMIN2, X X X Zone #1 or Zone #2 minimum
CFMZMIN outside air (cfm, L/s)
QRA1,QRA2,QRA X X X X Zone #1 or Zone #2 duct sensible
heat gain ([degrees]F,
[degrees]C)
ZRADB1,ZRADB2, X X X X Zone #1 or Zone #2 return air
dry-bulb temperature
([degrees]F, [degrees]C)
ZRADB
RABPNF X X Return air pressure before the
return fan (psi, kPa)
CFMRA X X X Return airflow rate (cfm, L/s)
RADBNF X X Return air dry-bulb temperature
before the return fan
([degrees]F, [degrees]C)
RAW X X X Combined return air humidity
ratio (lb/lb, g/kg)
MOTEFFR X X Electric motor efficiency of the
return fan (%)
RSHAFTR X X Calculated return fan energy use
(hp, kW)
RADB X X X Return air dry-bulb temperature
after the return fan
([degrees]F, [degrees]C)
RABP X X X Return air pressure after the
return fan (psi, kPa)
OAWB X X X X Outside air wet-bulb temperature
([degrees]F, [degrees]C)
OADB X X X X Outside air dry-bulb temperature
([degrees]F, [degrees]C)
OAW X X X X Outside air humidity ratio
(lb/lb, g/kg)
CFMOA X X X X Outside airflow rate (cfm, L/s)
MADB X X X Mixed air dry-bulb temperature
([degrees]F, [degrees]C)
MAW X X X Mixed air humidity ratio
(lb/lb, g/kg)
CFMMA X X X Mixed airflow rate (cfm, L/s)
QPH X Calculated load on the
preheating coil (Btu/h, kW)
CCEADB X X X X Cooling coil entering air
dry-bulb temperature
([degrees]F, [degrees]C)
CCEAW X X Cooling coil entering air
humidity ratio (lb/lb, g/kg)
PHLADB X Preheat coil leaving air
dry-bulb temperature
([degrees]F, [degrees]C)
PHLAW X Preheat coil leaving air
humidity ratio (lb/lb, g/kg)
PHLABP X Preheat coil leaving air
barometric pressure (psi, kPa)
MOTEFF X X X X Motor efficiency of the supply
fan (%)
RSHAFT X X X X Calculated fan energy use
(hp, kW)
QCL X X X X Calculated latent load on the
cooling coil (Btu/h, kW)
QCS X X X X Calculated sensible load on the
cooling coil (Btu/h, kW)
QHC X X X X Calculated load on the heating
coil (Btu/h, kW)
CFMT X X X X Calculated total airflow
(cfm, L/s)
CFMTD X X X X Design total airflow (cfm, L/s)
CFMZD1,CFMZD X X X Design airflow for zone #1
(cfm, L/s)
CFMZD2 X Design airflow for zone #2
(cfm, L/s)
CFMZ1 X Calculated airflow for zone #1
(cfm, L/s)
CFMZ2 X Calculated airflow for zone #2
(cfm, L/s)
SADB X Supply air dry-bulb temperature
([degrees]F, [degrees]C)
SAW X Supply air humidity ratio
(lb/lb, g/kg)
QRHCZ1,QRHCZ2 Reheat coil load for zone #1 or
zone #2 (Btu/h, kW)
PHLASP X Preheat leaving air setpoint
temperature ([degrees]F,
[degrees]C)
CCLASP,CCLAMIN X X Cooling coil leaving air
setpoint, or minimum
temperature ([degrees]F,
[degrees]C)
CFMSA X Supply airflow rate (cfm, L/s)
HCEADB X X Heating coil entering air
dry-bulb temperature
([degrees]F, [degrees]C)
HCEAW X X Heating coil entering air
humidity ratio (lb/lb, g/kg)
HCLASP X Heating coil leaving air
setpoint temperature
([degrees]F, [degrees]C)
HCLADB X X X Heating coil leaving air
dry-bulb temperature
([degrees]F, [degrees]C)
HCLAW X X X Heating coil leaving air
humidity ratio (lb/lb, g/kg)
HCCFM X Heating coil airflow rate
(cfm, L/s)
HCLABP X X X Heating coil leaving air
barometric pressure (psi, kPa)
CCCFM X X X Cooling coil airflow rate
(cfm, L/s)
CCLADB X X X X Cooling coil leaving air
dry-bulb temperature
([degrees]F, [degrees]C)
CCLAW X X X X Cooling coil leaving air
humidity ratio (lb/lb, g/kg)
HCCFM1,HCCFM2 X Heated airflow rate for zone #1
or zone #2 (cfm, L/s)
CCCFM1,CCCFM2 X Cooled airflow rate for zone #1
or zone #2 (cfm, L/s)
IUCFM X Induction unit airflow rate
(cfm, L/s)
IUCCLADB X Induction unit cooling coil
leaving air dry-bulb
temperature ([degrees]F,
[degrees]C)
IUCCLAW X Induction unit cooling coil
leaving air humidity ratio
(lb/lb g/kg)
IUHCLADB X Induction unit heating coil
leaving air dry bulb
([degrees]F, [degrees]C)
IUHCLAW X Induction unit heating coil
leaving air humidity ratio
(lb/lb, g/kg)
IUMIXLADB X Induction unit mixed air
leaving air dry bulb
([degrees]F, [degrees]C)
IUMIXLAW X Induction unit mixed air leaving
air humidity ratio
(lb/lb, g/kg)
IUMIXCFM X Induction unit mixed airflow
rate (cfm, L/s)
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temperature [K] 
density [kg/m3] 
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