Development of a Micro-Channel Evaporator Model for a CO2 Mobile Air-Conditioner

2000 ◽  
Author(s):  
M.-H. Kim ◽  
J. M. Yin ◽  
C. W. Bullard ◽  
P. S. Hrnjak
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Mass Transfer Process ◽  
Micro Channel ◽  
Air Conditioner ◽  
Air Conditioning System ◽  
Side Pressure ◽  
Volume Method ◽  
Energy Balances

Abstract This paper presents the development and verification of a heat exchanger model for evaluating thermal performance of an evaporator for a CO2 mobile air-conditioning system. The model has been developed, based on the finite volume method, with emphasis on the air-side heat and mass transfer process. The governing equations are derived from mass and energy balances using newly developed air-side heat transfer and friction loss correlations for micro-channel heat exchangers under dry and wet conditions. The calculated air-side heat transfer and pressure drop data are in good agreement with measured data. However, the refrigerant-side pressure drop estimation for micro-channel tubes usually underestimates the measured value. The simulation results and importance of selecting appropriate heat transfer and pressure drop correlations for the micro-channel heat exchanger are addressed.

Impact of an Anisotropic Fin Surface Design on the Thermal-Hydraulic Performance of a Plain-Fin-and-Tube Heat Exchanger

2011 ◽  
Author(s):  
Rong Yu ◽  
Andrew D. Sommers ◽  
Nicole C. Okamoto ◽  
Koushik Upadhyayula
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Heat Exchangers ◽  
Hydraulic Performance ◽  
Normal Operation ◽  
Surface Design ◽  
Tube Heat Exchanger ◽  
Silane Coating ◽  
Side Pressure

In this study, we have explored the effectiveness of heat exchangers constructed using anisotropic, micro-patterned aluminum fins to more completely drain the condensate that forms on the heat transfer surface during normal operation with the aim of improving the thermal-hydraulic performance of the heat exchanger. This study presents and critically evaluates the efficacy of full-scale heat exchangers constructed from these micro-grooved surfaces by measuring dry/wet air-side pressure drop and dry/wet air-side heat transfer data. The new fin surface design was shown to decrease the core pressure drop of the heat exchanger during wet operation from 9.3% to 52.7%. Furthermore, these prototype fin surfaces were shown to have a negligible effect on the heat transfer coefficient under both dry and wet conditions while at the same time reducing the wet airside pressure drop thereby decreasing fan power consumption. That is to say, this novel fin surface design has shown the ability, through improved condensate management, to enhance the thermal-hydraulic performance of plain-fin-and-tube heat exchangers used in air-conditioning applications. This paper also presents data pertaining to the durability of the alkyl silane coating.

Heat Transfer Experiments of Ethylene Glycol-Water Mixture in Multi-Port Serpentine Meso-Channel Heat Exchanger Slab

2010 ◽  
Author(s):  
Mesbah G. Khan ◽  
Amir Fartaj
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Ethylene Glycol ◽  
Test Fluid ◽  
Water Mixture ◽  
Micro Channel ◽  
Working Fluids ◽  
Micro Channels

In past few years, narrow diameter flow passages (≤3 mm) have attracted huge research attentions due to their several advantageous features over conventional tubes (≥6 mm) especially from the view points of higher heat transfer, lesser weight, and smaller device size. Several classifications of narrow channels, based on sizes, are proposed in the open literature from mini to meso and micro (3 mm to 100 μm). The meso- and micro-channels have not yet entered into the HVAC and automotive heat exchanger industries to the expected potentials to take the above-mentioned advantages. The reasons may be the limited availability of experimental data on pressure drop and heat transfer and the lack of consolidated design correlations as compared to what is established for compact heat exchangers. While a number of studies available on standalone single straight channels, works on multi-channel slab similar to those used as typical thermal heat exchanger core elements are inadequate, especially the research on multichannel serpentine slab are limited in the open literature. The 50% ethylene glycol and water mixture is widely used in heat exchanger industry as a heat transfer fluid. Studies of pressure drop and heat transfer on this commercially important fluid using narrow tube multi-channel slab is scarce and the availability of experimental data is rare in the open literature. Conducting research on various shapes of meso- and micro-channel heat exchanger cores using a variety working fluids are a definite needs as recommended and consistently urged in ongoing research publications in this promising area. Under present long-term project, an automated dynamic single-phase experimental infrastructure has been developed to carryout the fluid flow and heat transfer research in meso- and micro-channel test specimens and prototype microchannel heat exchanger using a variety of working fluids in air-to-liquid crossflow orientation. In the series, experiments have been conducted on 50% ethylene glycol and water solution in a serpentine meso-channel slab having 68 individual channels of 1 mm hydraulic diameter to obtain the heat transfer data and the general pressure drop nature of the test fluid. Current paper presents the heat transfer characteristics of ethylene glycol-water mixture and the Reynolds number effects on pressure drop, heat transfer rate, test specimen NTU and effectiveness, overall thermal resistance, and the Nusselt number.

Air-Side Heat Transfer Performance of Louver Fin and Multitube Heat Exchanger for Direct Methanol Fuel Cell Cooling Application

2014 ◽  
Vol 11 (4) ◽  
Author(s):  
Hie Chan Kang ◽  
Hyejung Cho ◽  
Jin Ho Kim ◽  
Anthony M. Jacobi
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Heat Exchangers ◽  
Direct Methanol Fuel Cell ◽  
Heat Transfer Performance ◽  
Transfer Performance ◽  
Side Pressure ◽  
Direct Methanol ◽  
Methanol Fuel Cell

The present work is performed to evaluate the heat transfer performance of a heat exchanger used in a direct methanol fuel cell. Because of material constraints and performance requirements, a louver fin heat exchanger is modified for use with conventional microchannel tubes and also with multiple small-diameter tubes (called multitubes). Prototype heat exchangers are tested, and the air-side heat transfer, pressure drop, and fan power are measured in a wind tunnel and simulated using a commercial code. The air-side pressure drop and heat transfer coefficient of the multitubes show similar trends to those of the flat-tube heat exchanger if the contact resistance is negligible. The tube spacing of the prototype multitube heat exchangers has a small effect on the pressure drop and heat transfer, but it has a profound effect on the air-side heat transfer performance because of the contact resistance between the tubes and louver fins. The air-side pressure drop agrees well with an empirical correlation for flat tubes.

scholarly journals Air-side performance of a micro-channel heat exchanger in wet surface conditions

2017 ◽  
Vol 21 (1 Part A) ◽  
pp. 375-385 ◽  
Author(s):  
Raviwat Srisomba ◽  
Lazarus Asirvatham ◽  
Omid Mahian ◽  
Ahmet Dalkılıç ◽  
Mohamed Awad ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Relative Humidity ◽  
Operating Conditions ◽  
Inlet Temperature ◽  
Micro Channel ◽  
Surface Conditions ◽  
Air Inlet ◽  
Wet Surface

The effects of operating conditions on the air-side heat transfer, and pressure drop of a micro-channel heat exchanger under wet surface conditions were studied experimentally. The test section was an aluminum micro-channel heat exchanger, consisting of a multi-louvered fin and multi-port mini-channels. Experiments were conducted to study the effects of inlet relative humidity, air frontal velocity, air inlet temperature, and refrigerant temperature on air-side performance. The experimental data were analyzed using the mean enthalpy difference method. The test run was performed at relative air humidities ranging between 45% and 80%; air inlet temperature ranges of 27, 30, and 33?C; refrigerant-saturated temperatures ranging from 18 to 22?C; and Reynolds numbers between 128 and 166. The results show that the inlet relative humidity, air inlet temperature, and the refrigerant temperature had significant effects on heat transfer performance and air-side pressure drop. The heat transfer coefficient and pressure drop for the micro-channel heat exchanger under wet surface conditions are proposed in terms of the Colburn j factor and Fanning f factor.

Thermal-Fluid Characteristics of an Automotive Radiator Used as the External Heat Exchanger in an Auto Air Conditioning System

2005 ◽  
Author(s):  
Amir Jokar ◽  
Mohammad H. Hosni ◽  
Steven J. Eckels
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Thin Plate ◽  
Air Conditioning ◽  
External Heat ◽  
Air Conditioning System ◽  
Louvered Fins ◽  
External Heat Exchanger ◽  
Fluid Characteristics

The thermal-fluid characteristics of an automotive radiator, used as the external heat exchanger in an auto air conditioning system, are experimentally analyzed and discussed in this article. The radiator in this study is a compact heat exchanger with parallel rectangular minichannels and louvered thin-plate fins. A 50% glycol-water mixture flows through the minichannels with staggered surface enhancements on the walls. On the other side, air flows through the radiator openings with the louvered thin-plate fins sandwiched between the minichannels. Single-phase heat transfer and pressure drop correlations for glycol-water flow within the minichannels and for air flow through the louvered fins are obtained and presented. The Wilson plot technique is applied to find the heat transfer coefficients on both the glycol-water and air sides. The frictional pressure drop for the glycol-water flow within the minichannels is also obtained using the Fanning equation. The uncertainty estimates for both measured and calculated parameters are then presented, and finally the results are plotted, discussed and compared with the relevant previous studies. These results show that the heat transfer rate is increased in the glycol-water side due to the surface enhancements in comparison with smooth rectangular channels. The heat transfer is enhanced on the air side as well, as compared with the flat smooth surfaces, due to the use of louvered fins.

Experimental Investigation of Flat Tube-Louver Fin Heat Exchanger Performance Working as a Cooler in Dry and Wet Conditions

2012 ◽  
Author(s):  
Sahil Popli ◽  
Yunho Hwang ◽  
Reinhard Radermacher
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Water Flow Rate ◽  
Ambient Air ◽  
Water Cooling ◽  
Air Velocity ◽  
Flat Tube ◽  
Side Pressure ◽  
Dry And Wet Conditions

An experimental study has been conducted to evaluate the performance of a flat-tube louver-fin heat exchanger working as a cooler, with frontal area of 0.25 m2 in both dry and wet conditions. Deluge water cooling at different flow rates was achieved by incorporating perforated tube-type distributor on top of the heat exchanger. Water at 35°C temperature was used as heat transfer fluid at cooler inlet. Ambient air and deluge cooling water were both maintained at 22°C temperature. Heat exchanger capacity and air-side pressure drop were measured with the heat exchanger angle set at 0° and 21° from vertical, with a frontal air velocity of 1.4 m/s and 3.5 m/s without deluge water cooling, and a frontal air velocity of 1.2 m/s, 1.4 m/s with deluge water cooling. Significant capacity enhancement could be obtained both with the use of deluge water cooling and with the heat exchanger angle set at 21° from vertical. Furthermore, it was found that approximately same capacity was obtained at both 0° and 21° angle when wetting water flow rate was reduced from 0.17 kg/s to 0.063 kg/s, without significant reduction in air-side pressure drop. This study highlights the importance of wetting of heat transfer surfaces of compact flat tube heat exchangers and provides motivation for further research in this area.

Modified Manifold-Microchannel Heat Exchangers Fabricated Based on Additive Manufacturing: Experimental Characterization

2019 ◽  
Author(s):  
William C. Yameen ◽  
Nathan A. Piascik ◽  
Andrew K. Miller ◽  
Riccardo C. Clemente ◽  
Jingru Z. Benner ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Additive Manufacturing ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Heat Flow ◽  
Heat Exchangers ◽  
Original Design ◽  
Flow Rates ◽  
Side Pressure ◽  
Manifold Microchannel

Abstract In this study, the additive manufacturing technique has been utilized to fabricate air-water heat exchangers for the application of thermoelectric power plants. Additive manufacturing is a powerful fabrication method that has enabled fabrication of complex geometries that are either challenging or impossible to fabricate based on conventional techniques. Three manifold-microchannel heat exchangers with different interior designs were fabricated by additive manufacturing and from stainless steel. The heat exchangers were tested at different air flow rates and different inlet water temperatures. One heat exchanger was designed and fabricated based on an original design of the manifold-microchannel heat exchanger. Two other heat exchangers were designed with some modifications compared to the original design. In one modified heat exchanger, cylindrical pin arrays were considered on air manifold walls in order to enhance air disturbance, and thus, increase heat transfer between water and air. The second modified heat exchanger contained same pins and also had microchannels in the perpendicular orientation compared to the original design in the outlet manifolds. This design modification was done in order to reduce air-side pressure drop in the heat exchanger. The heat transfer characteristics along with air-side pressure drop were measured and compared with the original design of the manifold-microchannel heat exchanger. Results indicated that the heat flow rate, convection heat transfer coefficient, and pressure drop did not significantly change in modified heat exchangers. For air Reynolds number between around 800 and 4,000, the heat flow rates obtained in the original heat exchanger (type A) and for 50° C water inlet temperature were between 63.9 and 228 W for the lowest and the highest air flow rates, respectively. For the same inlet water temperature, these heat flow rates were between 64.2 and 211 W for the lowest and the highest air flow rates and in one of the modified heat exchangers (type B), respectively. Similarly, while the highest air-side pressure drop in the original heat exchanger was 3458 Pa, this property was measured at 3525 (type B) and 3884 (type C) for the two modified heat exchangers.

RESEARCH OF HEAT TRANSFER AND PRESSURE DROP CHARACTERISTIC OF CONCAVO-CONVEX PLATE

2013 ◽  
Vol 21 (02) ◽  
pp. 1350012 ◽  
Author(s):  
AKIRA KANEKO ◽  
MASAFUMI KATSUTA ◽  
YUKI HAMANO
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Performance Improvement ◽  
System Performance ◽  
Air Conditioning ◽  
Parallel Plates ◽  
Pump System ◽  
Air Conditioning System ◽  
Heat Pump System

For an automobile air-conditioning system, performance improvement of the heat exchanger is needed to fit in the change of refrigerant and heat pump system. In this study, the heat transfer and pressure drop characteristic of air flow between parallel plates with concavity and convexity is grasped, and the possibility of using a fin-less heat exchanger is considered analytically. And it has been shown that a fin-less heat exchanger has the possibility of increasing performance compared to a conventional heat exchanger, which uses a corrugated louver fin.

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