Performance of series fan-powered terminal units with electronically commutated motors.
Variable-air-volume (VAV) systems maintain space conditions by varying the volume of conditioned air delivered to a space. A VAV system typically consists of several components starting at a central air handler unit (AHU), where cooling coils cool and dehumidify the primary air. This conditioned air, referred to as primary air, is delivered by the AHU central supply fan through a single-duct supply system to VAV terminal units. These terminal units are ducted to air outlets usually serving multiple offices or open areas in a building. Terminal units with a fan are called fan-powered terminal units (FPTU) and offer several advantages over terminal units without fans (ASHRAE 2008). FPTUs provide better mixing of the air induced from the plenum space with the primary air and allow the downstream air pressure to be increased to service rooms that might be short of air. Because the fan in the FPTU can be operated independently of the primary air handler, perimeter zones can be heated during unoccupied hours (ASHRAE 2008).
[FIGURE 1 OMITTED]
When the fan in a VAV fan-powered terminal unit is in series with the primary air (Figure 1), the unit is referred to as a series fan-powered terminal unit. In series units, the terminal unit fan must be in operation for air to be delivered to the space. The primary air inlet damper modulates the amount of primary air delivered to the space to maintain the temperature setpoint. The inlet air velocity sensor provides data on the primary airflow supplied to the series unit. Electric resistance or hot water coils (not shown in Figure 1) can be used to provide supplemental terminal reheat. Because the fan in a series FPTU is in series with the primary air handler, the air pressure for the primary air can be decreased compared to operation with a parallel FPTU (ASHRAE 2008).
It is important to be able to characterize individual terminal units to properly model a VAV system in a building energy use simulation. Complete system models based on measured performance data of fan-powered terminal units have only recently been made available for use in building simulation programs by Furr et al. (2008a; 2008b), who developed performance models for parallel and series fan-powered terminal units that had silicon-controlled rectifier (SCR) fan motors. Manufacturers also sell FPTUs with newer electronically commutated motors (ECMs). Because ECMs allow the FPTU to vary fan airflow by changing fan motor speed in response to changes in zone loads in a building, FPTUs with ECMs are expected to use less energy than older style SCR FPTUs. This paper includes performance data on eight FPTUs that cover two duct sizes, three manufacturers, and two ECM manufacturers.
Experimental Setup and Procedure
Furr et al. (2008c) described in detail the experimental setup and methodology used to test and characterize the performance of series and parallel SCR-controlled fan-powered terminal units. A brief description of the setup and test procedure is provided here. The basic test setup used for airflow measurements in this study is shown in Figure 2. Airflow was controlled and measured using nozzle airflow chambers (AMCA 1999) located both upstream and down-stream of the FPTU. Each chamber had a booster fan controlled by a variable speed drive (VSD). Nozzle combinations differed between each chamber and were selected by the operator. As the cumulative nozzle diameter was increased, less pressure was required to attain the same volumetric airflow through the chamber.
The two airflow chambers and FPTU were connected with sheet-metal ductwork. The length of this duct followed the specifications outlined in ASHRAE Standard 130 (2006). Tests were also done with only ductwork connected between the two airflow chambers to compare the airflow measurements between the two chambers. For the airflow ranges used for this study, the two chambers agreed within [+ or -] 3%.
Airflow quantities were calculated using the techniques found in AMCA Standard 210 (1999). The upstream airflow chamber was used to measure the primary air into the FPTU. Airflow values were adjusted to standard temperature and pressure conditions to compensate for environmental changes in the laboratory during the days of data collection. Induced airflow into the FPTU was calculated as the difference of the airflow measured with the upstream and downstream airflow chambers.
ASHRAE Standard 130 (2006) also dictated that the static pressure measurements be located specific distances (2.5 duct diameters downstream and 1 duct diameter upstream) from the FPTU. Static pressures were averaged across the respective cross-sections both upstream and down-stream of the terminal unit.
[FIGURE 2 OMITTED]
FPTUs typically share three common elements. Incoming primary air is received via an inlet duct with an inlet air velocity pressure ([P.sub.iav) sensor, which is a multi-point device that averages pressure over four locations across the duct. A second common element is a mechanical damper which regulates the flow rate of primary air and helps set the pressure differential across the entire terminal unit. Dampers typically come in either butterfly or opposing blade configurations. Modulation of these dampers is typically achieved using an electrically controlled actuator with a 0 to 10 VDC range that provides for operation from fully open to fully closed. The third common element is the fan, whose location inside the terminal unit varies by manufacturer. Parallel FPTUs also have a backdraft damper that is used to prevent air from leaking in through the induction port when the FPTU fan is not running.
Electrical performance data were recorded with a power quality analyzer. Current transformers rated for 0-5A were selected and had a [+ or -] 1% full scale accuracy. The current trans-formers were applied to both the power and neutral wires of the single-phase 277 VAC input. The simultaneously measured and recorded data included, but were not limited to: real and apparent power, RMS voltage (VRMS) and current (IRMS), associated harmonics, and total harmonic distortion. The data files were cached in the power quality analyzer's internal memory and then transferred to a personal computer.
A factorial test matrix spanning several independent variables was established for the FPTU designs to adequately span the expected range of operation in the field. Table 1 shows the independent variables and their ranges for this study.
Table 1. Series Fan-Powered Terminal Unit Test Matrix Independent Variable Test Points Value Range D, damper position 4 100%, 75%, 50%, 25% open Vfan, fan input voltage (ECM) 4 100%, 75%, 50%, 25% full scale Pup, upstream static 6 0.0-2.0 in. w.g. (0-498 Pa) Pdown, downstream static 1 0.25 in. w.g. (62 Pa)
The damper position, D, varied for the respective FPTU designs. Orientation was controlled using a damper actuator with a 0 to 10 VDC input that could vary the damper position between 100% fully open and fully closed. The fully closed condition was not included in the test matrix because this damper position would have produced no primary airflow, regardless of upstream pressure. The three manufacturers that provided terminal units for this study were designated as manufacturer A, B, and C. Two inlet sizes were evaluated: 8 in. (203 mm) and 12 in. (304 mm). Each terminal unit was labeled according to primary air inlet size and manufacturer. For example, an 8 in. (203 mm) terminal unit from manufacturer A was labeled as ECM_S8A. Manufacturer C provided units with ECM motors from two motor manufacturers. These terminal units were also differentiated by brand of ECM motor, either M1 or M2. Thus, a 12 in. (304 mm) terminal unit with an ECM motor from manufacturer M1 was labeled ECM_S12C-M1.
RESULTS AND MODELS
One of the goals of this study was to develop semi-empirical models for ECM series FPTUs similar to those previously developed for SCR series FPTUs by Furr et al. (2008a). These models had to provide sufficient characterization of the FPTUs so they could be used in building simulation models.
During testing, there were several operational problems with some FPTUs. For example, it was observed that under some conditions, the terminal unit fan would stop and run backward. It was also observed that when the ECM controller was turned to its highest setting for some FPTUs, the fan sometimes pulsed or cycled on and off. Because these operational problems were typically outside the manufacturer's recommended operating range, the data collected for these conditions were not used for any of the data analysis. However, these problems could be experienced in a field application if the installer and/or operator did not stay within the recommended operating range of static pressure or fan speed specified by the manufacturer.
Terminal Unit Airflow
Series terminal units require that the fan operate continuously to supply air to the conditioned space. If the primary airflow is lower than the air being supplied by the terminal unit fan, additional air can be drawn in from the plenum. Both the primary airflow delivered to the FPTU and the air delivered by the FPTU fan are variables that needed to be quantified.
The primary air supplied to the FPTU was modeled as a function of the pressure differential (DP) across the FPTU and the air inlet damper position. In this study, the differential pres-sure is defined as the difference in the upstream (primary air) static pressure and the downstream (supply air) static pressure of the terminal unit.
Manufacturers who provided units for this study used either butterfly or opposing blade designs for their primary air inlet dampers. During testing, both types of dampers were set at 100% open, 75% open, 50% open, and 25% open. Manufacturer C used an opposed blade damper for both brands of motors. In this case, 0[degrees] indicated a fully open damper, while 45[degrees] represented a fully closed damper. Both manufacturers A and B used a butterfly damper. In that case, 0[degrees] indicated a fully open damper, while 90[degrees] represented a fully closed damper.
Figure 3 shows the plot of primary air versus the differential pressure for the 8 in. (203 mm) series FPTU from manufacturer C, using motor M2. Figure 4 shows a similar plot for the 12 in. (304 mm) series FPTU from manufacturer A. The curves in both figures were generated from a best fit of the data to Equation 1. In this equation, C1, C2, and C3 were constants deter-mined from the regression analysis, S was the damper position (in degrees), and DP was the differential pressure defined earlier. The form of Equation 1 was originally developed by Furr et al. (2008a). The primary airflow delivered to the FPTU was proportional to the square root of the differential pressure across the terminal unit at a given damper setting. Because the downstream static pressure was maintained at 0.25 in. w.g. (62.3 Pa) for all of the tests, the DP required an offset to keep the value inside the square root positive. Furr et al. (2008a) determined that an offset of 0.27 in. w.g. (67.3 Pa) best fit the empirical data, and the same offset was used in this study to maintain model consistency. If the static pressure internal to the FPTU were measured and used in the model, it is likely that no offset would be needed. While it might also improve the series FPTU primary air model, no FPTU manufacturers provide static pressure taps at this location.
[Q.sub.primary] =[C.sub.1] * (1+[C.sub.2] * S + [S.sub.3]*[S.sup.2])* square root of (term)] D P + 0.27 (1)
The coefficients of the model for the different terminal units tested, as well as the R2 values, are presented in Table 2. The results for FPTU ECM_S8C-M1 were measured by Cramlet (2008). The measured data correlated well with Equation 1. The R2 values for the ECM-controlled FPTUs ranged from 0.895 to 0.977 and were comparable to those reported by Furr et al. (2008a) for SCR series FPTUs.
Table 2. Model Coefficients for ECM-Controlled Series FPTUs FPTU [C.sub.1] [C.sub.2 [C.sub.3] [R.sup.2] ECM_S8A 1637 -1.95E-02 7.80E-05 0.955 ECM_S12A 5109 -2.15E-02 1.14E-04 0.946 ECM_S8B 2094 -2.83E-02 2.06E-04 0.962 ECM_S12B 5886 -3.17E-02 2.54E-04 0.895 ECM_S8C-M1 2344 -3.84E-02 4.15E-04 0.977 ECM_S8C-M2 1895 -3.58E-02 3.70E-04 0.951 ECM_S12C-M1 5125 -3.09E-02 1.28E-04 0.927 ECM_S12C-M2 4561 -1.86E-02 -1.71E-04 0.909
The airflow provided by the fan in an ECM series FPTU is mainly a function of the ECM input setting. Figures 5 and 6 show fan airflow versus inlet velocity pressure for FPTUs ECM_S8B and ECM_S12C-M2, respectively. As seen in both figures, the FPTUs also showed a slight dependence on inlet air velocity pressure, [P.sub.iav].
[FIGURE 3 OMITTED]
[FIGURE 4 OMITTED]
These results were similar to those obtained by Furr et al. (2008a) who found that fan airflow was primarily dependent on the SCR voltage which controlled fan speed and showed a much smaller dependence on [P.sub.iav].
One reason for the similar results was the design of the series terminal units. Because upstream airflow and pressure have little effect on the internal static pressure, the fan operates with approximately the same pressure differential over a wide range of operating conditions. In addition, for ECM units, the electronically commutated motor was designed to maintain constant airflow for a given ECM input setting despite changes in operating conditions. Results for the other ECM series FPTUs were similar to those shown in Figures 5 and 6.
The model used to fit the fan airflow data is shown in Equation 2 and was similar to that used by Furr et al. (2008a). The results for all the ECM series units are shown in Table 3. Overall, the model correlated well with the data, with the lowest R2 value being 0.987 for ECM_S8A.
Table 3. Coefficients for Fan Airflow Model for ECM-Controlled Series FPTUs FPTU [C.sub.1] [C.sub.2] [C.sub.3] [C.sub.4] [R.sup.2] ECM_S8A 58.92 0.016 8.50 6.60 0.987 ECM_S12A 148.92 0.025 20.24 43.50 0.996 ECM_S8B -90.80 -0.052 21.41 20.12 0.991 ECM_S12B 375.12 0.015 11.59 -32.31 0.993 ECM_S8C-M1 108.30 0.0113 12.30 12.44 0.997 ECM_S8C-M2 -82.18 -0.043 18.18 34.25 0.992 ECM_S12C-M1 467.40 0.025 15.48 26.10 0.995 ECM_S12C-M2 67.43 -0.000787 21.47 75.60 0.997
[Q.sub.fan] = [C.sub.1] + [C.sub.2] * [V.sub.fan.sup.2] + C.sub.2] * [V.sub.fan] + [C.sub.4]*[P.sub.iav] (2)
[FIGURE 5 OMITTED]
[FIGURE 6 OMITTED]
For both the SCR and ECM units, the fan airflow was dependent on the inlet air velocity pressure, [P.sub.iav]. However, there was a major difference between the SCR and ECM correlations concerning the definition of the fan voltage. For the SCR correlations presented by Furr et al. (2008a), the fan volt-age was the AC voltage provided by the SCR to the fan motor. In the ECM models, the fan voltage was the percentage of the voltage between the minimum and maximum ECM settings on the controller.
The reason for using percentages for the ECM units instead of DC voltages was because manufacturers had different ways of specifying the input to the ECM controllers. For example, manufacturer A provided a controller that was adjusted by turning a set screw to change the setting from 0 to 100%, so settings of 25%, 50%, 75%, and 100% were used. FPTUs from manufacturer B had a 2 to 10 VDC input, so settings of 4 VDC (25%), 6 VDC (50%), 8 VDC (75%), and 10 V DC (100%) were used when varying the speed of the fan with the controller. Manufacturer C provided a controller that was adjusted using a 0 to 10 VDC signal, so settings of 2.5 VDC (25%), 5 VDC (50%), 7.5 VDC (75%), and 10 VDC (100%) were used. Table 4 contains a summary of the ECM settings for each manufacturer.
Table 4. Summary of ECM Settings for the Three Manufacturers FPTU Manufacturer ECM Settings 25% 50% 75% 100% A 25% 50% 75% 100% B 4 VDC 6 VDC 8 VDC 10 VDC C 2.5 VDC 5 VDC 7.5 VDC 10 VDC
Terminal Unit Power Performance
Both power consumption and power factor were measured. A model was developed for the power consumption as a function of ECM setting and inlet air velocity pressure, [P.sub.iav] Because the fan airflow was mainly controlled by the fan speed, which, in turn, was controlled by the ECM setting, the model used the ECM setting rather than fan airflow as an input. Power consumption was also influenced by downstream static pressure and the primary airflow. Because downstream pres-sure remained constant, it was not used in the model. The impact of primary airflow on the power consumption was modeled by including Piav.
The power consumption of the VAV fan was mainly dependent on the airflow it produced. The airflow was almost entirely dependent on the ECM setting, and because the ECM setting was an input into the system, it was used for modeling rather than the airflow. It also showed a small dependence on primary airflow, which was represented by Piav. Figure 7 shows the fan power versus the airflow of the fan for terminal unit ECM_S8C-M2, while Figure 8 shows these data for terminal unit ECM_S12C-M1.
[FIGURE 7 OMITTED]
[FIGURE 8 OMITTED]
The power curves for all the ECM series terminal units were similar in form to those shown in Figures 7 and 8. Power varied approximately with the square of the airflow. The main difference between the data in Figures 7 and 8 and the power data obtained by Furr et al. (2008a) for SCR series units was that the power was nearly linear with respect to the SCR fan airflow, while it was quadratic for the ECM series units. Figure 9 shows a comparison of power consumption for SCR_S12A from Furr et al. (2008a) and ECM_S12A from this study. At the lowest flow rate for the SCR unit, which was about 850 f[t.sup.3]/min (0.40 [m.sup.3]/s), it consumed approximately 370 W of power. In contrast, the ECM unit at the same airflow consumed approximately 70 W. Thus, at low flow conditions, the SCR unit used over five times as much power as the ECM unit. As the fan airflow rates increased, as shown in Figure 9, the difference in power consumption between the SCR and ECM units narrowed. However, when the SCR unit is initially installed in a building, its speed would be set by the installer to meet the maximum (or design) load conditions in the space. It would then run continuously at that speed whenever the HVAC system is operating even though load conditions in the space may be light compared to the maximum conditions. In contrast, the ECM unit would vary its speed to meet lighter (or heavier) load conditions. As a consequence, the savings in fan power with the ECM FPTU can be potentially higher than in the example discussed above. A building simulation model would have to be used to estimate the savings with an ECM or a SCR series unit.
The fan power model used for the ECM-controlled fans was similar to that used for the SCR-controlled units (Equation 3) except for the definition of the fan voltages. For the SCR units, the fan voltae represented the AC voltage measured after the SCR controller. For the ECM units, the fan voltage represented the percent of maximum ECM setting. Table 5 presents the coefficients for the ECM terminal units. The model produced satisfactory results for the ECM units, with the lowest R2 being 0.968. Overall, the model from Furr et al. (2008a), with the appropriate modifications for the definition of fan voltage, appeared to correlate the power consumption of the ECM motors as well as it did the SCR motors reported by Furr et al. (2008a).
Table 5. Fan Power Model Coefficients for ECM Series Terminal Units FPTU [C.sub.1] [C.sub.2] [C.sub.3] [C.sub.4] [R.sup.2] ECM_S8A 70.34 0.049 -2.602 2.34 0.968 ECM_S12A 197.65 0.161 -9.589 24.38 0.989 ECM_S8B 8.89 0.061 -0.221 21.26 0.985 ECM_S12B 112.28 0.074 -3.657 -31.92 0.978 ECM_S8C-M1 79.00 0.0705 -3.150 -12.99 0.998 ECM_S8C-M2 46.61 0.045 -1.165 -4.71 0.993 ECM_S12C-M1 145.83 0.111 -4.310 -45.40 0.998 ECM_S12C-M2 179.66 0.131 -7.303 -18.47 0.996
[FIGURE 9 OMITTED]
Powe[r.sub.fan] =[C.sub.1] + [C.sub.2] * [V.sub.fan.sup.2] + [C.sub.3] * [V.sub.fan] + [C.sub.4] * [P.sub.iav] (3)
For the ECM-controlled FPTUs, the power factor typically varied between 0.4 and 0.6, regardless of the ECM setting. Each individual motor seemed to react differently to increasing ECM settings, with no consistent trend. Table 6 shows how the power factor varied for ECM_S8B and ECM_S12C-M1. For ECM_S8B, the power factor increased with ECM setting, while it decreased for ECM_S12C-M1. For each of the FPTUs, the power factors were averaged over the whole range of ECM settings. The results are shown in Table 7. With the exception of ECM_S8C_M2, the 8 in. (203 mm) FPTUs generally had smaller power factors than the 12 in. (304 mm) units. Motor manufacturer M2 had slightly higher power factors than the same FPTU with motor/controllers from manufacturer M1. While the ECM units measured here had lower power factors than those of the SCR units, the overall impact on the building power factor may still be smaller for ECM units because of the significantly reduced overall power consumption during off-peak conditions. The detailed comparison would require use of a building simulation program, which was beyond the scope of this paper.
Table 6. Power Factors for ECM_S8B and ECM_P12A or Different ECM Settings Power Factor ECM Setting ECM_S8B ECM_S12C-M1 25% 0.40 0.51 50% 0.42 0.52 75% 0.42 0.49 100% 0.43 0.48 Table 7. Average Power Factors for Each of the CM Fan-Powered Terminal Units Unit Average Power Factor ECM_S8A 0.40 ECM_S8B 0.42 ECM_S8C_M1 0.44 ECM_S8C_M2 0.54 ECM_S12A 0.51 ECM_S12B 0.43 ECM_S12C-M1 0.50 ECM_P12C-M2 0.54
SUMMARY AND CONCLUSION
An integral part of every VAV system is the terminal unit. Some applications use fan-powered terminal units, which come in either series or parallel configurations. Furr et al. (2008a) developed detailed performance models for fan power terminal units that had SCR-controlled motors. This study extended the work of Furr et al. (2008a) to eight series ECM-controlled fan-powered terminal units from three terminal unit and two motor manufacturers. The overall trends in performance of the ECM-controlled FPTUs were similar among the units evaluated. Semi-empirical models of the same form used by Furr et al. (2008a) were applied in this study to satisfactorily represent the different performance characteristics of the ECM-controlled FPTUs.
Each series unit needed three models to characterize its performance. The first was the primary air performance, which was independent of fan voltage. This model had R2 values that ranged from 0.895 to 0.962 for the ECM units. The series model could possibly be improved by using the internal FPTU static pressure to calculate the differential pressure used in the model instead of the static pressure downstream of the fan.
The second model developed for the series fan-powered terminal units was the airflow provided by the terminal unit fan. For the ECM-controlled units, the R2 values of this model ranged from 0.987 to 0.997. Furr et al. (2008a) reported that the model also correlated highly for the SCR-controlled units, with R2 values ranging from 0.989 to 0.997 for properly functioning SCR controllers. The exceptionally high R2 values for this form of the model demonstrate that it explains most of the variability in the data.
The third model developed for the series units was that of fan power consumption. This was an important model because ECM-controlled fans are expected to perform much better than their SCR counterparts. This model also correlated well with the data for the ECM units. R2 values ranged from 0.968 to 0.988. These R2 values were similar to those reported by Furr et al. (2008a) for SCR series FPTUs. This model can be used in conjunction with the fan airflow model to compare the power consumption of ECM- and SCR-controlled units at different operating conditions.
The data and models provided in this study should also allow an engineer to determine if an ECM series FPTU would be more energy efficient than an SCR series or parallel FPTU for a given application. These models should allow development of better air system models in building simulation programs. The actual implementation or integration of these models into one of the popular building simulation programs is left to the engineers and scientists who maintain and upgrade those programs.
The authors wish to thank the following individuals and organizations who provided support and advice for this proj-ect: Gus Faris of Nailor Industries, David John of Metal Indus-tries, Inc., Dan Int-Hout of Krueger Manufacturing Co., Ron Jordan and Doug Fetters of A.O. Smith Electrical Products Company, Floyd Blackwell of Regal Beloit Corporation, Gaylon Richardson of Engineered Air Balance Co., Inc., and Jack Stegall of Energistics Laboratory.
DP = Pressure differential across the terminal unit, in. w.g. (Pa)
[P.sub.down] = Downstream (supply air) static pressure, in. w.g (Pa)
[P.sub.iav] = Pressure across inlet air differential (velocity) flow sensor, in. w.g. (Pa)
[P.sub.unit] = Static pressure inside terminal unit, in. w.g. (Pa)
[P.sub.up] = Upstream (primary air) static pressure, in. w.g. (Pa)
[P.sub.owerfan]= Power consumption of terminal unit fan, W
[Q.sub.fan] = Amount of airflow through terminal unit fan, f[t.sup.3]/min ([m.sup.3]/s)
[Q.sub.induced] = Amount of airflow induced from plenum, f[t.sup.3]/min ([m.sup.3]/s)
[Q.sub.supply] = Amount of parallel terminal unit airflow output, f[t.sup.3]/min ([m.sup.3]/s)
[Q.sub.primary ]= Amount of primary airflow, f[t.sup.3]/min ([m.sup.3]/s)
S = Damper setting, degrees
[V.sub.rms] = RMS average of AC voltage used by the terminal unit, V
[V.sub.fan ]= Input voltage (in percentage of full scale) for ECM units, %
Kenneth Elovitz, Professional Engineer, Energy Economics, Inc., Foxboro, MA: How did you coordinate the ECM speed with the downstream airflow chamber so only the downstream chamber measured and did not affect the ECM fan airflow?
Dennis O'Neal: Both the upstream and downstream airflow chambers had booster fans with variable speed drives. The speed of these fans could be adjusted during tests to compensate for either more or less pressure loss through the chamber nozzles, screens, etc. For most tests, the static pressure down-stream of the fan-powered terminal unit was fixed at a certain value. As the airflow setting on the fan-powered terminal unit was adjusted, the speed of the booster fan would be adjusted, so the downstream static pressure remained at the specified value for the tests. In this way, the fan-powered terminal unit always sensed the same downstream static pressure over its range of airflow settings.
AMCA. 1999. ANSI/AMCA Standard 210-99. Laboratory Methods of Testing Fans for Aerodynamic Performance
Rating. Arlington Heights, IL: Air Movement and Control Association.
ASHRAE. 2006. ANSI/ASHRAE Standard 130-1996 (RA 2006). Methods of Testing for Rating Ducted Air Terminal Units. Atlanta: American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc.
ASHRAE. 2008. Room air distribution equipment. In
ASHRAE Handbook--HVAC Systems and Equipment. Atlanta: American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc.
Cramlet, A. 2008. Performance of ECM controlled VAV fan powered terminal units. M. Sc. Thesis, Texas A&M University, College Station, TX.
Davis, M., J. Bryant, and D.L. O'Neal. 2009. Modeling the performance of single-duct VAV systems that use fan powered terminal units. ASHRAE Transactions: Sympo-sia 115(1).
Furr, J., D.L. O'Neal, M. Davis, J.A. Bryant, and A. Cramlet. 2008a. Performance of VAV fan powered terminal units: Experimental results and models for series units.
ASHRAE Transactions 114(1).
Furr, J., D.L.O'Neal, M. Davis, J.A. Bryant, and A. Cramlet. 2008b. Performance of VAV fan powered terminal units:
Experimental results and models for parallel units ASHRAE Transactions 114(1).
Furr, J., D.L. O'Neal, M. Davis, J. Bryant, and A. Cramlet. 2008c. Performance of VAV fan powered terminal units: Experimental setup and methodology. ASHRAE Trans-actions 114(1).
Jacob L. Edmondson Dennis L. O'Neal, PhD, PE Associate Member ASHRAE Fellow ASHRAE John A. Bryant, PhD, PE Michael A. Davis, PhD Member ASHRAE Member ASHRAE
Jacob L. Edmondson is a mechanical engineer, E.I.T., with Goetting and Associates, San Antonio, TX. Dennis L. O'Neal is Holdredge/Paul Professor and head of the Department of Mechanical Engineering, Texas A&M University, College Station, TX. John A. Bryant is an associate professor at Texas A&M University at Qatar, Doha, Qatar. Michael A. Davis is the director of laboratories at New York University Abu Dhabi, Abu Dhabi, United Arab Emirates.
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|Author:||Edmondson, Jacob L.; O'Neal, Dennis L.; Bryant, John A.; Davis, Michael A.|
|Date:||Jul 1, 2011|
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