Unit Cell Model Formulation and Thermal Performance Analysis for Cross-Flow Heat Exchanger

2016 ◽  
Author(s):  
Hengyun Zhang ◽  
Zhaoqiang Wang ◽  
Yansong Wang
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Thermal Performance ◽  
Cell Model ◽  
Cross Flow ◽  
Volume Averaging ◽  
Unit Cell ◽  
Unit Cell Model ◽  
Flow Heat ◽  
The Cross

An analysis for the cross-flow heat exchanger is conducted for electronic cooling applications, with the design goal of dissipating 175W from high power chip by maintaining the chip temperature within 85 °C in a compact space. Liquid to liquid heat exchanger in cross flow arrangement is preferred due to its compact size and high effectiveness. A volume averaging formulation is developed to determine the heat transfer coefficient at the unit cell level. The effects of channel shape, channel size, and heat exchanger material are examined through the heat transfer in the unit cell model. The obtained heat transfer coefficients are also used for the estimation of the heat exchanger thermal performance based on the effectiveness-NTU method. To verify the volume averaging formulation, a full field heat and fluid flow over the cross-flow heat exchangers are investigated through numerical computation. The amount of heat exchanged is extracted and compared with the unit cell model prediction. A fairly good agreement is obtained between the two approaches. Fabrication of cross-flow heat exchanger is further discussed to meet the design target.

Cross-Flow Heat Exchanger: Volume-Averaging Formulation of a Unit Cell Model and Thermal Performance Analysis

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
Hengyun Zhang ◽  
Zhaoqiang Wang
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Thermal Performance ◽  
Cell Model ◽  
Cross Flow ◽  
Volume Averaging ◽  
Unit Cell ◽  
Unit Cell Model ◽  
Flow Heat ◽  
The Cross

A formulation of the unit cell model and the corresponding thermal performance analysis for the cross-flow heat exchanger are carried out, with the design goal of dissipating 175 W from a high-power electronic chip in a compact space. A liquid to liquid heat exchanger in the cross-flow arrangement is preferred due to its compact size and high effectiveness. The unit cell model is formulated based on the volume-averaging method to determine the heat transfer coefficient involving two heat exchanging fluids and a solid. The various factors such as channel shape, channel edge length, channel size, and heat exchanger material can be examined based on the unit cell model. The obtained heat transfer coefficients are used for the estimation of the heat exchanger thermal performance based on the effectiveness–number of transfer units (NTU) correlation. To verify the model formulation, the heat and fluid flow over the cross-flow heat exchangers are investigated through the full-field numerical computation. The amount of heat exchanged from the numerical computation is extracted and compared with the predicted results from the unit cell model. A fairly good agreement is obtained between the two approaches. Based on the unit cell model, an aluminum cross heat exchanger with eight channel layers for the hot and cold fluids, 15 channels in each layer with a channel diameter of 2 mm, is able to meet the design target.

scholarly journals Fluid flow consideration in fin-tube heat exchanger optimization

2010 ◽  
Vol 31 (3) ◽  
pp. 87-104 ◽  
Author(s):  
Piotr Wais
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Heat Exchanger ◽  
Mass Flow ◽  
Cross Flow ◽  
Finned Tube ◽  
Tube Heat Exchanger ◽  
Flow Heat ◽  
The Cross ◽  
Fin Tube

Fluid flow consideration in fin-tube heat exchanger optimizationThe optimization of finned tube heat exchanger is presented focusing on different fluid velocities and the consideration of aerodynamic configuration of the fin. It is reasonable to expect an influence of fin profile on the fluid streamline direction. In the cross-flow heat exchanger, the air streams are not heated and cooled evenly. The fin and tube geometry affects the flow direction and influences temperature changes. The heat transfer conditions are modified by changing the distribution of fluid mass flow. The fin profile impact also depends on the air velocity value. Three-dimensional models are developed to find heat transfer characteristics between a finned tube and the air for different air velocities and fin shapes. Mass flow weighted average temperatures of air volume flow rate are calculated in the outlet section and compared for different fin/tube shapes in order to optimize heat transfer between the fin material and air during the air flow in the cross flow heat exchanger.

scholarly journals Performance Analysis of a Countercurrent Flow Heat Exchanger Placed on the Truck Compartment Roof

2012 ◽  
Vol 4 (4) ◽  
Author(s):  
Wamei Lin ◽  
Jinliang Yuan ◽  
Bengt Sundén
Keyword(s):  
Heat Exchanger ◽  
Thermal Performance ◽  
Cross Flow ◽  
Countercurrent Flow ◽  
Position Change ◽  
Power Requirement ◽  
Ansys Fluent ◽  
Pin Fin ◽  
Flow Heat ◽  
The Cross

Due to the increasing power requirement and the limited available space in vehicles, placing the heat exchanger at the roof or the underbody of vehicles might increase the possibility to handle the cooling requirement. A new configuration of the heat exchanger has to be developed to accommodate with the position change. In this paper, a countercurrent heat exchanger is developed for position on the roof of the vehicle compartment. In order to find an appropriate configuration of fins with high thermal performance on the air side, the computational fluid dynamics approach is applied for a comparative study among louver fin, wavy fin, and pin fin by using ANSYS FLUENT software. It is found that the louver fin performs high thermal performance and low pressure drop. Thus, the louver fin is chosen to be the configuration of the countercurrent flow heat exchanger. It is also found that the countercurrent flow heat exchanger presents higher heat transfer coefficient than the cross flow heat exchanger. Furthermore, the overall size and the air pumping power of the countercurrent flow heat exchanger are lower than those in the cross flow heat exchanger. Several suggestions and recommendations are highlighted.

scholarly journals The Effect of Flowrate and Effectiveness on Theoretical Design and Thermal Characteristic of a GHE

2018 ◽  
Vol 225 ◽  
pp. 01023
Author(s):  
T.M. Yusof ◽  
M.F. Basrawi ◽  
A. Shahrani ◽  
H. Ibrahim
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Thermal Characteristic ◽  
Variable Parameter ◽  
Cross Flow ◽  
Outlet Temperature ◽  
Performance Study ◽  
Commercial Unit ◽  
Hot Climate ◽  
Flow Heat

Ground heat exchanger is an exciting technique to reduce energy consumption in building especially in hot climate countries. Implementation of GHE for commercial unit in Malaysia is almost none in record. Thus, performance study of the GHE in Malaysia is crucial to be conducted either experimentally or numerically. Therefore, this paper presents the performance of GHE in term of effectiveness, outlet temperature and rate of heat transfer based on mathematical model. The model is developed based on cross flow heat exchanger with one fluid unmixed. There are two variable parameter used in the analysis which is effectiveness and flowrate of the air for 25 meter length of a PVC pipe. Three effectiveness values which is 0.8, 0.9 and 0.99 have been analysed in this study. Meanwhile, flowrate of air is ranging from 0.02 to 0.2 kg/s. Results show that flowrate at 0.02 kg/s gives great temperature reduction in the pipe compared with higher flowrate. However, flowrate of 0.2 kg/s produces higher cooling potential. Characteristic of the GHE for the rate of heat transfer with 80, 90 and 99 percent effectiveness also have been developed and it has been found that effectiveness of 0.9 provide good combination between flowrate and the rate of heat transfer for 25 meter length of the pipe

scholarly journals Investigation of flow non-uniformities in the cross-flow heat exchanger with elliptical tubes

2019 ◽  
Vol 108 ◽  
pp. 01009 ◽  
Author(s):  
Stanisław Łopata ◽  
Paweł Ocłoń ◽  
Tomasz Stelmach
Keyword(s):  
Heat Exchanger ◽  
Measurement Data ◽  
Cross Flow ◽  
Flow Distribution ◽  
Transitional Flow ◽  
Working Fluid ◽  
Elliptical Cross ◽  
Flow Heat ◽  
The Cross ◽  
Inflow Conditions

In heat exchangers, especially those with the cross-flow arrangement, it is nearly impossible to achieve the uniform distribution of the working fluid in the tubular space with the currently used inlet and outlet chambers (in some constructions as well). The improper inflow conditions to individual tubes, including those with an elliptical cross-section - often used because of their favorable features compared to round tubes, is the cause of improper heat transfer. In this respect, transitional flow is of particular importance. This flow regime is complex and challenging to model. Therefore, it is necessary to perform experimental verification. For this purpose, an appropriate stand was built, allowing to investigate the flow of the working fluid (water) to the elliptical tubes in the cross-current heat exchanger. The paper presents the results of measurements for manifold geometry, which are currently used in practice (for heat exchanger constructions). The analysis of the measurement data confirms the nonuniform flow distribution to individual tubes of the heat exchanger.

Performance Analysis of Multi-Pass Cross-Flow Heat Exchangers

2018 ◽  
Author(s):  
Kiran Lankalapalli ◽  
Ahmed ElSawy ◽  
Stephen Idem
Keyword(s):  
Heat Exchanger ◽  
Performance Analysis ◽  
Thermal Performance ◽  
Heat Exchangers ◽  
Cross Flow ◽  
Threshold Value ◽  
Finned Tube ◽  
Flow Heat ◽  
Rate Ratios ◽  
Side Flow

A steady state sensible performance analysis of multi-pass cross-flow finned-tube heat exchangers is reported. The investigation considers various flow circuiting, such as counter cross-flow, parallel cross-flow, and cross-flow where the tube-side flow is in parallel. A previously developed matrix approach is used to evaluate the heat exchanger performance in each tube pass. The equations required to model the thermal performance of these configurations are presented, and the thermal performance is compared for each type of flow circuiting. Thereafter a parametric study on cross-flow heat exchanger performance is performed by varying physically significant parameters such as number of transfer units (NTU) and capacity rate ratios, and the graphical results for each type of flow circuiting are presented both for both two-pass and three-pass arrangements. A consistent criterion is proposed for each case, wherein increasing the NTU beyond a certain threshold value does not significantly improve heat exchanger thermal performance.

Transient Turbulent Flow and Heat Transfer Phenomena in Plate-Fin Type Cross-Flow Heat Exchanger

2011 ◽  
Vol 32 (1) ◽  
pp. 20-32 ◽  
Author(s):  
Isak Kotcioglu ◽  
Ahmet Cansiz ◽  
Sinan Caliskan ◽  
Senol Baskaya
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Turbulent Flow ◽  
Cross Flow ◽  
Flow And Heat Transfer ◽  
Flow Heat
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