Refrigerant distribution in minichannel evaporator manifolds.Received November 15, 2006; accepted January 18, 2007
The effects of geometry and operating conditions on the distribution of refrigerant re·frig·er·ant
1. Cooling or freezing; refrigerating.
2. Reducing fever.
1. A substance, such as air, ammonia, water, or carbon dioxide, used to provide cooling either as the working substance of R-410A in heat exchangers heat exchanger
Any of several devices that transfer heat from a hot to a cold fluid. In many engineering applications, one fluid needs to be heated and another cooled, a requirement economically accomplished by a heat exchanger. with horizontal manifolds This is a list of particular manifolds, by Wikipedia page. See also list of geometric topology topics. For categorical listings see and its subcategories. Generic families of manifolds
1. Orient The countries of Asia, especially of eastern Asia.
a. The luster characteristic of a pearl of high quality.
b. A pearl having exceptional luster.
3. minichannels were experimentally investigated to provide the essential design information for the minichannel evaporators. Flow visualization In fluid dynamics it is critically important to see the patterns produced by flowing fluids, in order to understand them. We can appreciate this on several levels: Most fluids (air, water, etc. in the horizontal manifold manifold
In mathematics, a topological space (see topology) with a family of local coordinate systems related to each other by certain classes of coordinate transformations. Manifolds occur in algebraic geometry, differential equations, and classical dynamics. showed that the flow patterns of the two-phase refrigerant before and after the liquid-vapor transition are in stratified stratified /strat·i·fied/ (strat´i-fid) formed or arranged in layers.
Arranged in the form of layers or strata. flow for the end-inlet location and in bubbly and stratified flows for the side-inlet location. Test results showed that the normalized standard deviation In statistics, the average amount a number varies from the average number in a series of numbers.
(statistics) standard deviation - (SD) A measure of the range of values in a set of numbers. of the liquid mass flow rate, which indicates the degree of maldistribution mal·dis·tri·bu·tion
Faulty distribution or apportionment, as of resources, over an area or among a group. , changes from 0.088 to 0.263 with manifold 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. location changes, from 0.034 to 0.141 with manifold inlet mass flow rate changes, from 0.037 to 0.082 with tube number changes, and from 0.027 to 0.055 with tube pitch changes. The normalized standard deviation of the liquid mass flow rates showed that the liquid refrigerant flow distribution is strongly affected by the manifold inlet location and the manifold inlet mass flow rate but is primarily independent of tube pitch. The side-inlet location showed a better liquid refrigerant flow distribution than the end-inlet location by more effectively mixing of the liquid and the vapor refrigerant from the inlet. Therefore, the side-inlet location is preferred to the end-inlet location.
The two basic demands for air-conditioning and refrigeration refrigeration, process for drawing heat from substances to lower their temperature, often for purposes of preservation. Refrigeration in its modern, portable form also depends on insulating materials that are thin yet effective. systems are improving the efficiency and reducing the size of the equipment. Compact heat exchangers, especially aluminumbrazed heat exchangers, meet these demands very well. As manufacturing technology in aluminum-brazed compact heat exchangers advances, the hydraulic diameter The hydraulic diameter, , is a commonly used term when handling flow in noncircular tubes and channels. Using this term one can calculate many things in the same way as for a round tube. of the tube channel has been reduced to a size of less than 1 mm. The reduced cross-sectional area of each tube requires many parallel tubes to keep the pressure drop across the heat exchangers within a reasonable range. Having many parallel tubes leads to refrigerant maldistribution issues when the minichannel heat exchanger is used as an evaporator evaporator
Industrial apparatus for converting liquid into gas or vapour. The single-effect evaporator consists of a container or surface and a heating unit; the multiple-effect evaporator uses the vapour produced in one unit to heat a succeeding unit. . Refrigerant flow maldistribution is defined as a nonuniform distribution of the liquid flow rates. Since refrigerant maldistribution causes an overall deterioration de·te·ri·o·ra·tion
The process or condition of becoming worse. of the heat exchanger performance, it is essential to understand the optimal design parameters and operating conditions.
Many researchers experimentally and numerically investigated this issue of refrigerant maldistribution in the evaporator for conventional and minichannel heat exchangers, as summarized in Table 1. Several researchers investigated two-phase distribution in manifolds with branch tubes (Horiki and Osakabe 1999; Kariyasaki et al. 1995; Rong et al. 1995; Zietlow et al. 2002; Tompkins et al. 2002; Lee and Lee 2005; Webb and Chung 2005; Watanabe et al. 1995a, 1995b; Asoh et al. 1991; Vist and Pettersen 2004; Fei et al. 2002; Sa et al. 2003; Cho et al. 2002; Vist 2004), most of which were conducted with air/water or low vapor pressure vapor pressure, pressure exerted by a vapor that is in equilibrium with its liquid. A liquid standing in a sealed beaker is actually a dynamic system: some molecules of the liquid are evaporating to form vapor and some molecules of vapor are condensing to form liquid. fluorocarbons. Only a few works were conducted with high-pressure working fluids such as R-22 and [CO.sub.2] (Sa et al. 2003; Cho et al. 2002; Vist 2004). It has been reported that gravity is an important force affecting the two-phase distribution in horizontal manifolds with vertical branch tubes. In a manifold with upward branch tubes, vapor flows predominantly through the branch tubes near the inlet, while liquid flows through the branch tubes near the far end of the manifold. Although many authors reported experimental measurements for the two-phase refrigerant distribution in the manifold, there are few works published regarding experimental measurements under realistic operating conditions, with realistic geometry and with R-410A as a working fluid. The objective of the current study is to provide essential design information through an experimental study of the effects of the geometry of the heat exchangers and operating conditions on the distribution of refrigerant R-410A in heat exchanger manifolds.
Table 1. Summary of Previous Works on Two-Phase Flow Distribution Authors Heat Flow Working Inlet Exchanger Direction Fluids Conditions in Manifold and Tubes Horiki and Square HM-VUT Air-water Adiabatic Osakabe(1999) manifold (40 x 40 mm) with4 tubes ([D sub.i] 10 mm) Kariyasaki et Manifold HM-VUT Air-water Adiabatic al. (1995) ([D.sub.i] 13.9 mm) with 3 tubes ([D sub.i] 4.3 mm) Rong et al. Plate HX HM-VDT Air-water Quality: (1995) with 7 HM-VUT 0-0.22 tubes Adiabatic Zietlow et al. Manifold HM-VDT Air-water MFR: 20 g/s (2002) with 19 Quality: 0.18 tubes Adiabatic Tompkins et Manifold ([D HM-VDT Air-water MF: 50-400 al. (2002) sub.i] 14 kg/[m.sup.2] mm) with 15 s Quality: minichannel 0-1 tubes (6 Adiabatic ports, [D sub.i] 1.6 and 19.1 mm width) Lee and Lee Manifold ([D VUM-HT Air-water MF: 70-165 (2005) sub.i] 14 kg/[m.sup.2] s mm) with 15 Quality: flat tubes 0.3-0.7 (11.6 mm Adiabatic width, 1.4 mm height, 10 mm intervals) Webb and Chung D-shape HM-VDT Air-water MFR: 10-60 (2005) manifold HM-VUT g/s Quality: with 20 0.3-0.8 minichannel Adiabatic tubes (11 ports [D.sub.hi] 1.3 and 25.4 mm width) Watanabe et Manifold ([D HM-VUT R-11 MFR: al. (1995a) sub.i] 20 12.6-37.7 g/s mm) with 4 Quality: tube ([D 0-0.3HF: 0, sub.i] 6 and 6.25, 12.5 40 mm kW/[m.sup.2] intervals) Watanabe et Manifold ([D HM-VUT R-11 MF: 40-120 al. (1995b) sub.i] 20 HM-HT (VT), 440-620 mm) with n (HT) tubes ([D kg/[m.sup.2] sub.i] 6 and s Quality: 40 mm subcool-0.4 intervals) Adiabatic (n: 2,3,4 (VT), 3,4,5 (HT)) Asoh et al. Manifold ([ HM-VDT R-113 MFR: 28-53 (1991) sup.i] 13.6 g/s Quality: mm) with 3 0.1-0.25 tubes ([ Heat: 80-230 sup.i] 4.5 W mm) Vist and Manifold ([D HM-VUT R-134a MFR: 2.5-4.2 Pettersen sub.i] 8 and g/s Quality: (2004) 16 mm) with 0.11-0.50 10 tubes ([D Pressure: sub.i] 4 mm, 690-710 kPa 21 mm tube pitch) Fei et al. Plate HX HM-VDT R-134a MFR: 20-60 (2002) with 5 g/s Quality: tubes 0-0.30 Pressure: 690-760 kPa Sa et al. Minichannel HM-VUT R-22 MFR: (2003) evaporator: 11.1-19.4 g/s manifold ([D Quality: 0.2 sub.i] 19.4 Pressure: 0.7 mm) with 15 MPa minichannel tubes (8 ports, [D.sub.hi] 1.2 mm) Cho et al. Manifold ([D VM-HT R-22 MF: 60 (2002) sub.i] 19.4 kg/[m.sup.2] mm) with 32 s Quality: minichannel 0.1-0.3 tubes (10 Pressure: ports, HD 0.62 MPa 1.5 mm) Adiabatic Vist and Manifold ([D HM-VUT [CO.sub.2] MFR: 2.3-4.2 Pettersen sub.i] 8 and g/s Quality: (2003) 16 mm) with 0.11-0.50 10 tubes ([D Pressure: sub.i] 4 5.5-5.6 MPa mm)
An experimental facility with a flow visualization section mimicking a real heat exchanger manifold geometry was developed. Figures 1 and 2 show 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 of the experimental setup and an exploded ex·plode
v. ex·plod·ed, ex·plod·ing, ex·plodes
1. To release mechanical, chemical, or nuclear energy by the sudden production of gases in a confined space: diagram of the flow visualization section, respectively. The setup was composed of four major parts: the main refrigerant circuit, the test heat exchanger section with distributing manifold visualization Using the computer to convert data into picture form. The most basic visualization is that of turning transaction data and summary information into charts and graphs. Visualization is used in computer-aided design (CAD) to render screen images into 3D models that can be viewed from all , the post-heater section to measure mass flow rates and vapor qualities Steam Engines use water vapor to drive pistons which effects work through movement. The quality of steam can be quantitatively described. Vapor quality is a quantitative description of the usefulness of a vapor to do work. of the individual tube groups, and the condensing con·dense
v. con·densed, con·dens·ing, con·dens·es
1. To reduce the volume or compass of.
2. To make more concise; abridge or shorten.
a. unit circuit. The pre-heater at the inlet of the test section was used to heat the subcooled liquid If the temperature of the liquid is lower than the saturation temperature for the existing pressure, it is called either a subcooled liquid (implying that the temperature is lower than the saturation temperature for the given pressure) or a compressed liquid (implying that the refrigerant to the desired inlet vapor quality. The branch tubes were heated by tape heaters. The refrigerant flow through each branch tube group in the heat exchanger was directed by three-way ball valves ball valve
A valve regulated by the position of a free-floating ball that moves in response to fluid or mechanical pressure. to either the collecting tube or the post-heater section. The distributing manifold was clear plastic and circular in shape with an inner diameter of 19.0 mm. Minichannel tubes were inserted into the centerline cen·ter·line
1. A line that bisects something into equal parts.
2. A painted line running along the center of a road or highway that divides it into two sections for traffic moving in opposite directions, or, in the case of of the manifold. The manifolds were installed in a horizontal position horizontal position,
n a posture in which the body lies flat and the feet and head remain on the same level. Also called
supine. with minichannel tubes of overall 1 m in length oriented in the vertically upward flow configuration. To measure the distribution characteristics along the distributing manifold, three branch tubes were grouped together at the collecting manifold using baffles. Tube groups were numbered sequentially from left to right. The minichannel tubes, which are shown in Figure 3, have six rectangular rec·tan·gu·lar
1. Having the shape of a rectangle.
2. Having one or more right angles.
3. Designating a geometric coordinate system with mutually perpendicular axes. ports of 1.70 mm hydraulic diameter. The inlet pipe inlet pipe n (Tech) → tuyau m d'arrivée
inlet pipe inlet n → Zuleitung f, Zuleitungsrohr nt
to the manifold was straight and ten times longer than the pipe inner diameter to ensure a fully developed flow that eliminates the impact of the upstream obstructions on the flow patterns. Measurements for the refrigerant distribution were conducted by measuring the mass flow rates and the vapor qualities of the individual tube groups. Uncertainties of the instruments are summarized in Table 2. Uncertainties of the manifold inlet vapor quality, the branch tube inlet vapor quality, and the branch tube mass flow rate (MFR MFR,
n See myofascial release. ) was [+ or -]0.01%, [+ or -]0.06%, and 0.35%, respectively.
[FIGURE 1 OMITTED]
[FIGURE 2 OMITTED]
[FIGURE 3 OMITTED]
Table 2. List of Instruments and Their Uncertainties Physical Instrument Range Uncertainty Parameter Temperature T-type -250[degrees]C [+ or -] thermocouple - 0.5[degrees]C 350[degrees]C Pressure Absolute 0-1,724 kPa [+ or -]0.11% pressure transducer Mass flow Coriolis mass 0-75 g/s [+ or -]0.1% rate flowmeter Heater Power meter 0-4 kW [+ or -]0.5% input
The flow in the distributing manifold was monitored, and the distribution of the refrigerant mass flow rate and the vapor quality was measured for each tube group while the operating conditions and the heat exchanger geometry were varied, as summarized in Table 3. The experimental parameters listed in Table 3 are applicable to a typical residential air-conditioning system.
Table 3. Range of Experimental Parameters Experimental Parameters Range Inlet temperature 7.2[degrees]C Inlet quality 0.3 Refrigerant R-410A Manifold inlet mass flow rate, g/s 30/45/60 Heat load, kW 0/5/10 Heat exchanger tube pitch, mm/tube 8/10/12 Location of inlet End/Side Number of heat exchanger tubes in parallel 18/24/30
With regard to the location of the inlet, the "end inlet" refers to the design with the inlet pipe located to the left side of the distributing manifold and aligned straight with the manifold centerline, while the "side inlet" refers to the design with the inlet pipe located in the middle of the manifold and aligned at a 90degree angle with the manifold centerline. The results of the refrigerant distribution in the distributing manifold are presented as the mass flow rate ratio (MFRR MFRR Maintenance Forms, Records and Reports ) of the vapor and the liquid phases in the ith branch tube group to total MFR as shown in Equation 1.
[R.sub.[bt,ph]](i)(%) = [[m.sub.[bt,ph]](i)/[N.summation summation n. the final argument of an attorney at the close of a trial in which he/she attempts to convince the judge and/or jury of the virtues of the client's case. (See: closing argument) over (i = 1)] [m.sub.[bt,ph]](i)] x 100 (1)
where ph = vap (vapor) and liq (liquid).
Flow Visualization Results
Figure 4 shows the flow pattern under adiabatic ad·i·a·bat·ic
Of, relating to, or being a reversible thermodynamic process that occurs without gain or loss of heat and without a change in entropy. conditions for two inlet locations and two mass flow rates. For the end-inlet location, "stratified flow" or "stratified-wavy flow" pattern was observed so that vapor and liquid flowed at the upper and lower part of the distributing manifold, respectively, due to the gravitational grav·i·ta·tion
a. The natural phenomenon of attraction between physical objects with mass or energy.
b. The act or process of moving under the influence of this attraction.
2. effect. This flow pattern matches one identified from the flow pattern maps provided by Kattan et al. (1998) and Thome et al. (2002). Based on visual observation, the profile of the liquid-vapor interface was of a "stepwise stepwise
incremental; additional information is added at each step.
stepwise multiple regression
used when a large number of possible explanatory variables are available and there is difficulty interpreting the partial regression " shape. The liquid level was almost constant and was located below the ends of the branch tubes near the inlet, while it was almost constant and was located above the ends of the branch tubes on the far end of the manifold. Between these two regions, there was a short transition area, where the liquid level increased abruptly a·brupt
1. Unexpectedly sudden: an abrupt change in the weather.
2. Surprisingly curt; brusque: an abrupt answer made in anger.
3. in a slope. As the refrigerant MFR increased, the liquid-vapor interface (shown in dashed line) traveled farther from the inlet due to a higher momentum. Based on the measurement for the ten branch tube groups under adiabatic conditions, the liquid-vapor interface for the MFRs, 30, 45, and 60 g/s, was located right after the branch tube group numbers, 1, 2, and 3, respectively. It should be noted that another transition seems to occur just under branch tube group number 4 in Figure 4, but this is due to the different reflection between the rear sight glass and the main body, which can be further explained by the exploded diagram of the flow visualization section shown in Figure 2.
[FIGURE 4 OMITTED]
For the side-inlet location, the incoming refrigerant impinged on the inner side wall of the manifold and was divided symmetrically sym·met·ri·cal also sym·met·ric
Of or exhibiting symmetry.
Adv. 1. near the inlet. The flow patterns of two-phase refrigerant were in a bubbly flow before the liquid-vapor transition and in a stratified flow after the liquidvapor transition. The liquid-vapor interface was in a V-shape near the inlet. As the refrigerant MFR increased, the vapor traveled farther toward both ends of the manifold and the liquid-vapor interface took on a wider V-shape. At the far end of the manifold, the liquid level of the liquid-vapor interface was almost constant and was above the ends of the branch tubes. For both inlet locations, the locations of the liquid-vapor interface were almost independent of tube pitch. Additionally, as the heat load increased, the liquid-vapor interface traveled slightly farther from the inlet.
Flow Distribution Results
Effects of Manifold Inlet Mass Flow Rate. Figure 5 shows the refrigerant distribution results under the condition of 5 kW heat load for two inlet locations and three mass flow rates. For the end-inlet location, the profile of the branch tube inlet vapor quality was in a "stepwise" shape. Two regions of almost constant value existed, with a very short transition region between the two regions--one of about 100% vapor quality near the inlet and another of about 12% vapor quality near the end of the manifold. As the manifold inlet mass flow rate increased, the number of branch tube groups with almost 100% tube inlet vapor quality also increased because the liquid-vapor interface was located closer to the end of the manifold due to the increased momentum. At a manifold inlet mass flow rate of 30 g/s, 10% of the branch tubes had almost 100% tube inlet vapor quality, and at 60 g/s, about 30% of the branch tubes had almost 100% tube inlet vapor quality. However, for the side-inlet location, there was no region with 100% branch tube inlet vapor quality; instead, the profile of the branch tube inlet vapor quality was symmetric No difference in opposing modes. It typically refers to speed. For example, in symmetric operations, it takes the same time to compress and encrypt data as it does to decompress and decrypt it. Contrast with asymmetric.
(mathematics) symmetric - 1. . The branch tube inlet vapor quality was about 60~70% near the inlet and about 20% near the end of the manifold. Between the two regions, the branch tube inlet vapor quality decreased steadily along the manifold.
[FIGURE 5 OMITTED]
For both inlet locations, the MFRRs deviated within a 2% range from the average MFRR. As the manifold inlet MFR increased, the MFRRs for the branch tube groups near the manifold inlet decreased slightly, while the MFRRs for the branch tube groups near the end of the manifold increased slightly because the liquid traveled farther due to the higher momentum. Moreover, the liquid MFRRs for the branch tube groups near the inlet were much lower than those for the branch tube groups located at the far end of the manifold. However, for the end-inlet location, approximately 7%~15% of the inlet manifold Noun 1. inlet manifold - manifold that carries vaporized fuel from the carburetor to the inlet valves of the cylinders
gasoline engine, petrol engine - an internal-combustion engine that burns gasoline; most automobiles are driven by gasoline engines liquid MFR flowed through the first three branch tube groups near the inlet. For the side inlet, about 25% of the inlet manifold liquid MFR flowed through the four branch tube groups near the inlet.
Effects of Heat Load. Figure 6 shows refrigerant distribution results under the 60 g/s MFR condition for the two inlet locations and three heat loads. For both inlet locations, the vapor quality along the branch tubes also increased as the heat load increased. As a result, the gravitational pressure drop along the branch tubes was reduced for the tubes located far from the inlet. Consequently, more liquid refrigerant flowed to the far end of the manifold, and the liquid-vapor interface was located farther from the inlet as the heat load increased. However, the overall effect of the heat load on the liquid refrigerant flow distribution was within the measurement error range, except at the branch tube groups near the liquid-vapor interface.
[FIGURE 6 OMITTED]
Effects of the Number of Branch Tubes. Figure 7 shows the refrigerant distribution results under the 55 g/s MFR condition for the two inlet locations and three sets of branch tubes, 18, 24, and 30 each. As shown in the figure, the vapor quality profiles of the reduced number of branch tubes were similar to that of the 30-tube configuration for both inlet locations. Additionally, the liquid MFRRs increased as the number of branch tubes decreased for both inlet locations due to fewer tubes at the fixed manifold inlet MFR. In order to analyze quantitatively the degree of maldistribution for the three tube numbers, the normalized standard deviation of the liquid MFR of the branch tube groups was evaluated by using Equation 2.
[FIGURE 7 OMITTED]
[MATHEMATICAL EXPRESSION A group of characters or symbols representing a quantity or an operation. See arithmetic expression. NOT REPRODUCIBLE IN ASCII ASCII or American Standard Code for Information Interchange, a set of codes used to represent letters, numbers, a few symbols, and control characters. Originally designed for teletype operations, it has found wide application in computers. ] (2)
[AMFR AMFR Autocrine Motility Factor Receptor .sub.liq] = [[N.sub.bt].summation over(i - 1)] [m.sub.bt,liq](i)/[N.sub.bt]
The smaller the value, the more uniform the distribution. The calculated values are noted in Table 4, which shows that the normalized standard deviations of the side-inlet location are smaller than those of the end-inlet location. For the end-inlet location, the 30-tube configuration has the lowest normalized standard deviation. For the side-inlet location, the 24-tube configuration has the lowest. Overall, the difference in the normalized standard deviations of the three configurations is within 0.1.
Table 4. Normalized Standard Deviation of Liquid MFR MFR 30g/s 55g/s Inlet Location End Inlet Side Inlet End Inlet Side Inlet Branch tube no.: 30 ea 0.408 0.320 0.549 0.286 Branch tube no.: 24 ea 0.450 0.235 0.595 0.202 Branch tube no.: 18 ea 0.466 0.256 0.631 0.249
Effects of the Tube Pitch. Figure 8 shows the refrigerant distribution at 55 g/s MFR and 5 kW heat load conditions for the two inlet locations and three tube pitches, 8, 10, and 12 mm. The figure shows that the vapor quality and the liquid MFRR distribution are barely affected by the variation of the tube pitch for both inlet locations. In order to assess quantitatively the degree of maldistribution for the three tube pitches, the normalized standard deviation of the liquid MFR at the branch tube groups was calculated as shown in Table 5. It can be concluded from these results that the vapor and liquid distribution in the manifold is barely affected by the variation of the tube pitch.
[FIGURE 8 OMITTED]
Table 5. Normalized Standard Deviation of Liquid MFR MFR 30 g/s 55 g/s Inlet Location End Inlet Side Inlet End Inlet Side Inlet Tube pitch: 10 mm 0.408 0.320 0.549 0.286 Tube pitch: 8 mm 0.438 0.354 0.580 0.294 Tube pitch: 12 mm 0.439 0.368 0.576 0.341
Since the state of the refrigerant entering the evaporator is in two-phase and the vapor quality of the refrigerant changes upon the operating conditions, the proper refrigerant distribution to a multiple number of tubes is a challenging task. In order to provide essential design information for the minichannel evaporators, an experimental study was conducted to determine the effects of geometry and operating conditions on the distribution of refrigerant in the horizontal evaporator manifold. Based on the observations made from the flow visualization and experimental data of the flow distribution, the following characteristics were observed.
* The gravitational force and the momentum difference between the liquid and the vapor phases affect the phase separation in the horizontal manifold. Low momentum vapor on the top layer is easily taken off in the branch tubes near the inlet, while the high momentum liquid on the bottom layer travels farther toward the far end of the manifold.
* For the end-inlet location, the profile of the branch tube inlet vapor quality is of a "stepwise" shape. As the manifold inlet mass flow rate increases, the number of branch tube groups having almost 100% tube inlet vapor quality also increases because the liquid-vapor interface is located closer to the end of the manifold due to the increased momentum. However, for the side-inlet location, there are no regions with 100% branch tube inlet vapor quality, and the profile of the branch tube inlet vapor quality is symmetric. The branch tube inlet vapor quality is about 60% to 70% near the inlet and about 20% near the end of the manifold. Between these two regions, the branch tube inlet vapor quality decreases steadily along the manifold.
* The normalized standard deviation of the liquid mass flow rate, which indicates the degree of maldistribution, changes from 0.088 to 0.263 with manifold inlet location changes, from 0.034 to 0.141 with manifold inlet mass flow rate changes, from 0.037 to 0.082 with tube number changes, and from 0.027 to 0.055 with tube pitch changes. Therefore, it can be concluded that the liquid refrigerant flow distribution is rather strongly affected by the manifold inlet location and the manifold inlet mass flow rate but is primarily independent of the tube pitch.
* Overall, the side-inlet location is preferred to the end-inlet location for the range of mass flow rates investigated.
This work was sponsored by the American 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 ASHRAE American Society of Heating, Refrigerating & Air Conditioning Engineers ), and the Center for Environmental Energy Engineering (CEEE CEEE Conference on Environmental Education in Europe
CEEE Co-Operation for Environmental Education in Europe ) at the University of Maryland University of Maryland can refer to:
1. A distinct group within a group; a subdivision of a group.
2. A subordinate group.
3. Mathematics A group that is a subset of a group.
tr.v. is gratefully acknowledged.
NOMENCLATURE nomenclature /no·men·cla·ture/ (no´men-kla?cher) a classified system of names, as of anatomical structures, organisms, etc.
AMFR = average mass flow rate
HM = horizontal flow in manifold
HL = heat load
HT = horizontal flow in tube
m = mass flow rate
MF = mass flux flux
In metallurgy, any substance introduced in the smelting of ores to promote fluidity and to remove objectionable impurities in the form of slag. Limestone is commonly used for this purpose in smelting iron ores.
MFR = mass flow rate
MFRR = mass flow rate ratio
N = number of tube group
NSTD NSTD New Systems Training Division
NSTD Nonsystem Training Devices
NSTD No Stranger to Debate
NSTD Network Service Technology Development (Sprint) = normalized standard deviation
R = ratio
TN = tube number
TP = tube pitch
VDT (Video Display Terminal) A terminal with a keyboard and display screen.
VDT - video display terminal = vertical downward flow in tube
VUT VUT Vanuatu (ISO Country code)
VUT Victoria University of Technology (now Victoria University)
VUT Vaal University of Technology (South Africa) = vertical upward flow in tube
VUM = vertical upward flow in manifold
x = vapor quality
bt = branch tube
dm = distributing manifold
liq = liquid
ph = phase
vap = vapor
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HTD Heat Transfer Division
HTD Haste the Day (band)
HTD High Torque Drive (synchronous belt drives)
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Rong, X., M. Kawaji, and J.G. Burgers Burgers are hamburgers.
Burgers may also refer to:
A plate heat exchanger is a type of heat exchanger that uses metal plates to transfer heat between two fluids. . ASME/JSME Fluid Engineering and Laser Anemometry an·e·mom·e·try
Measurement of wind force and velocity.
ane·mo·met Conference and Exhibition, August 13-18, Hilton Head, SC.
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Yunho Hwang, PhD Member ASHRAE
Dae-Hyun Jin, PhD Student Member ASHRAE
Reinhard Radermacher, PhD Fellow ASHRAE
Yunho Hwang is a research associate professor, Dae-Hyun Jin is a graduate research assistant, and Reinhard Radermacher is a professor in the Department of Mechanical Engineering at the University of Maryland, College Park The University of Maryland, College Park (also known as UM, UMD, or UMCP) is a public university located in the city of College Park, in Prince George's County, Maryland, just outside Washington, D.C., in the United States. , MD.