Statistical Determination of the Experimental Channels Clogging Rates in Mini- and Microchannel Heat Exchangers

2019 ◽  
Vol 142 (2) ◽  
Author(s):  
Witold Rybiński ◽  
Jarosław Mikielewicz
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Theoretical Model ◽  
Pressure Drop ◽  
Cold Water ◽  
Nondestructive Method ◽  
Microchannel Heat Exchanger ◽  
Statistical Determination ◽  
Experimental Values

Abstract This paper presents a new statistical, nondestructive method for determination of the experimental channels clogging rate in a mini- or microchannel heat exchanger. Channels clogging may be caused by inaccurate fabrication of the heat exchanger or by fouling of microchannels during exploitation. The theoretical model, used in this method, predicts a significant increase of the pressure drop as the number of clogged microchannels increases. However, the exchanger’s heat transfer rate decreases moderately. It may partly be caused by the additional heat transfer in metal walls, bypassing the inactive, clogged microchannels. The presented method was tested on the prototype of a microchannel heat exchanger. The experimental values of the pressure drop of the hot and cold water flows are 2–5 times higher than the values predicted for clean microchannels. The experimental values for the pressure drop and heat transfer are in good agreement with the values calculated by the use of the theoretical model. The presented statistical method gives two channels clogging rates (for the “hot” and “cold” channels) obtained during normal exploitation without cutting (destroying) the heat exchanger.

The Effect of Using Nanofluids on Triangular Microchannel Heat Exchanger Performance

2010 ◽  
Author(s):  
G. Bhaskaran ◽  
H. A. Mohammed ◽  
N. H. Shuaib
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Volume Fraction ◽  
Numerical Study ◽  
Particle Volume Fraction ◽  
Three Dimensional ◽  
Hydrodynamic Performance ◽  
Particle Volume ◽  
Microchannel Heat Exchanger

A numerical study is performed to study the effects of using various types of nanofluids on a triangular shaped microchannel heat exchanger (MCHE). The performance of an aluminum MCHE with various types of nanofluids such as Al2O3, CuO, SiO2, Ag and TiO2 and diamond particles with particle volume fraction of 2% using water as base fluid is comprehensively analyzed. The three-dimensional steady, laminar developing flow and conjugate heat transfer of a balanced MCHE were solved using finite volume method. In order to maintain laminar flow in the microchannels, Re number was ranged from 100 to 800. The other parameters tested in this study include the effects of Reynolds number towards the temperature, effectiveness and pressure drop of the MCHE. It is found that nanofluids have improved the temperature profile and heat transfer rate of the MCHE. The increase in pressure drop was minimal while the thermal and hydrodynamic performance of the heat exchanger was enhanced.

Numerical Simulation of Manifold Microchannel Heat Exchanger

2016 ◽  
Author(s):  
Muhammad Ansab Ali ◽  
Tariq S. Khan ◽  
Ebrahim Al Hajri
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Heat Transfer Rate ◽  
Heat Exchangers ◽  
Transfer Rate ◽  
Water Mixture ◽  
Microchannel Heat Exchanger ◽  
Compact Size

The quest to achieve higher heat transfer rate, smaller size and minimum pressure drop is a main area of focus in the design of heat exchangers. Plate heat exchangers are one of viable candidates to deliver higher heat duties but still have a drawback of higher pressure drop due to long restricted flow path. Motivated by demand of miniaturization and cost reduction, a novel design of tubular microchannel heat exchanger for single phase flow employing ammonia water mixture is proposed. Numerical simulation of unit fluid domain is conducted in ANSYS Fluent. Parametric study of the different flow geometries is evaluated in terms of Nusselt number and pressure drop. The salient features of the design include ultra-compact size with higher heat transfer rate and acceptable pressure drop.

Development of a Microchannel Heat Exchanger for Aerospace Applications

2012 ◽  
Author(s):  
Hal Strumpf ◽  
Zia Mirza
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Heat Exchangers ◽  
State Of The Art ◽  
Design And Optimization ◽  
Microchannel Heat Exchanger ◽  
Aerospace Applications ◽  
Accurate Design ◽  
Adjustment Factors

Honeywell Aerospace has been developing microchannel heat exchangers for aerospace use. These heat exchangers offer significant reduction in volume and some reduction in weight compared to state-of-the-art aerospace heat exchangers constructed using offset plate and fin interupted surfaces. A microchannel heat exchanger was designed based on the requirements and available envelope for an aerospce liquid-to-air heat exchanger presently in service. The new micochannel heat exchanger was fabricated and a full testing campaign was undertaken to validate the design approach and generate appropriate adjustment factors for pressure drop and heat transfer. Based on this correlated model, the heat exchanger was re-sized for the required conditions. This updated design shows a significant reduction in size compared to the existing heat exchanger. In addition, Honeywell now has a validated approach enabling accurate design and optimization of microchannel heat exchangers for diverse problem conditions.

Effect of Helical Screw Tape Insertion on Heat Transfer and Pressure Drop Characteristics in a Horizontal Concentric Double Tube Heat Exchanger

2014 ◽  
Vol 541-542 ◽  
pp. 622-627
Author(s):  
A.A. Kapse ◽  
P.R. Dongarwar ◽  
R.R. Gawande
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Cold Water ◽  
Hot Water ◽  
Full Length ◽  
Tube Heat Exchanger ◽  
Nusselt Numbers ◽  
Friction Factors ◽  
Plain Tube

In the present work, the effects of insertion of helical screw tape on heat transfer characteristics and pressure drop in a concentric double tube heat exchanger are experimentally investigated. The heat exchanger has the outer (steel) and inner (copper) tube diameters of 50 mm and 25 mm respectively. The helical screw tape of diameter 19 mm is inserted into the inner tube to increase turbulence which helped to increase the heat transfer rate. The hot water was flowed through the inner tube and cold water was flowed in annulus. The helical screw tape was inserted in 1/3rd length and full length of the tube. The experiments are based on Reynolds number at tube inlet, ranging from 10000 to 42855. The experimental results show that the average Nusselt numbers and friction factors are respectively, 1.41 and 2.08 times over the plain tube for 1/3rd length insert and 1.87 and 4.31 times over the plain tube for full length insert. Furthermore, the enhancement ratio of the helical screw tape varies between 1.03 and 1.17, 1.02 and 1.26 for 1/3rd length insert and full length insert, respectively.

Numerical simulation of the fluid flow and heat transfer characteristics of microchannel heat exchangers with different reentrant cavities

2019 ◽  
Vol 29 (11) ◽  
pp. 4334-4348
Author(s):  
Minqiang Pan ◽  
Hongqing Wang ◽  
Yujian Zhong ◽  
Tianyu Fang ◽  
Xineng Zhong
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Heat Exchangers ◽  
Heat Transfer Performance ◽  
Transfer Performance ◽  
Content Type ◽  
Microchannel Heat Exchanger ◽  
Flow And Heat Transfer

Purpose With the increasing heat dissipation of electronic devices, the cooling demand of electronic products is increasing gradually. A water-cooled microchannel heat exchanger is an effective cooling technology for electronic equipment. The structure of a microchannel has great impact on the heat transfer performance of a microchannel heat exchanger. The purpose of this paper is to analyze and compare the fluid flow and heat transfer characteristic of a microchannel heat exchanger with different reentrant cavities. Design/methodology/approach The three-dimensional steady, laminar developing flow and conjugate heat transfer governing equations of a plate microchannel heat exchanger are solved using the finite volume method. Findings At the flow rate range studied in this paper, the microchannel heat exchangers with reentrant cavities present better heat transfer performance and smaller pressure drop. A microchannel heat exchanger with trapezoidal-shaped cavities has best heat transfer performance, and a microchannel heat exchanger with fan-shaped cavities has the smallest pressure drop. Research limitations/implications The fluid is incompressible and the inlet temperature is constant. Practical implications It is an effective way to enhance heat transfer and reduce pressure drop by adding cavities in microchannels and the data will be helpful as guidelines in the selection of reentrant cavities. Originality/value This paper provides the pressure drop and heat transfer performance analysis of microchannel heat exchangers with various reentrant cavities, which can provide reference for heat transfer augmentation of an existing microchannel heat exchanger in a thermal design.

Pressure Drop and Heat Transfer Performance of Microchannel Heat Exchanger With Circular Reentrant Cavities and Ribs

2020 ◽  
Vol 142 (4) ◽  
Author(s):  
Tingbo Hou ◽  
Yuanlong Chen
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Heat Transfer Performance ◽  
Hot Water ◽  
Outlet Temperature ◽  
Transfer Performance ◽  
Microchannel Heat Exchanger ◽  
Outlet Pressure ◽  
Rib Arrangement

Abstract The rib arrangement has an important influence on the pressure drop and heat transfer performance of a microchannel heat exchanger (MHE) with circular reentrant cavities and ribs. In this study, four kinds of MHEs with circular reentrant cavity and ribs were designed, namely, circular reentrant cavities (circular), circular reentrant cavities and single-sided ribs (circular—single), circular reentrant cavities and odd-symmetric ribs (circular—odd), and circular reentrant cavities and double symmetric ribs (circular—double). The effect of the rib arrangement on the pressure drop and heat transfer performance of MHEs was numerically investigated by ansysfluent 15.0. The experimental platform was then designed and built for the subsequent experimental verification. The results showed that the pressure drop between the inlet and outlet of the MHE with circular reentrant cavities and ribs increased as the inlet flow increased. At the same inlet flowrate, the pressure drop between the inlet and outlet of the MHEs was largest for the circular reentrant cavities and double symmetric ribs, followed by the circular reentrant cavities and odd-symmetric ribs, circular reentrant cavities and single-sided ribs, and the circular reentrant cavities. The presence of the rib structure increased the inlet and outlet pressure drop of the MHE. The MHE with circular reentrant cavities and double symmetric ribs had the largest inlet and outlet pressure drop, followed by that with circular reentrant cavities and odd-symmetric ribs, that with circular reentrant cavities and single-sided ribs, and that with circular reentrant cavities, indicating that the latter exhibited the best pressure drop performance. At the same inlet flowrate, the MHE with circular reentrant cavities had the highest hot water outlet temperature and the MHE with circular reentrant cavities and double symmetric ribs had the lowest temperature, whereas the results were the opposite for the cold-water outlet temperature. This indicates that the heat transfer performance was best for the MHE with circular reentrant cavities and double symmetric ribs, followed by that with circular reentrant cavities and odd-symmetric ribs and that with circular reentrant cavities and single-sided ribs.

A Microchannel Heat Exchanger for Electronics Cooling Applications

2008 ◽  
Author(s):  
Joseph Dix ◽  
Amir Jokar ◽  
Robert Martinsen
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Heat Fluxes ◽  
Semiconductor Diode ◽  
Air Cooling ◽  
Heat Rejection ◽  
Micro Scale ◽  
Microchannel Heat Exchanger ◽  
Macro Scale

The power consumption of electronic devices, such as semiconductor diode laser bars, has continually increased in recent years while the heat transfer area for rejecting the associated thermal energy has decreased. As a result, the generated heat fluxes have become more intense making the thermal management of thes systems more complicated. Air cooling methods are not adequate for many applications, while liquid cooled heat rejection methods can be sufficient. Significantly higher convection heat transfer coefficients and heat capacities associated with liquids, compared to gases, are largely accountable for higher heat rejection capabilities through the micro-scale systems. Forced convection in micro-scale systems, where heat transfer surface area to fluid volume ratio is much higher than similar macro-scale systems, is also a major contributor to the enhanced cooling capabilities of microchannels. There is a balance, however, in that more power is required by microchannels due to the large amount of pressure drop that are developed through such small channels. The objective of this study is to improve and enhance heat transfer through a microchannel heat exchanger using the computational fluid dynamics (CFD) method. A commercial software package was used to simulate fluid flow and heat transfer through the existing microchannels, as well as to improve its designs. Three alternate microchannel designs were explored, all with hydraulic diameters on the order of 300 microns. The resulting temperature profiles were analyzed for the three designs, and both the heat transfer and pressure drop performances were compared. The optimal microchannel cooler was found to have a thermal resistance of about 0.07 °C-cm2/W and a pressure drop of less than half of a bar.

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