Experimental Study on Air Cooling via a Multiport Mesochannel Cross-Flow Heat Exchanger

2011 ◽  
Author(s):  
Sarbadaman Dasgupta ◽  
Faisal A. Siddiqui ◽  
Md. Abdul Quaiyum ◽  
Serena A. Al-Obaidi ◽  
Amir Fartaj
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Heat Exchanger ◽  
Thermal Resistance ◽  
Heat Exchangers ◽  
Cross Flow ◽  
Uniform Temperature ◽  
Flow Channels ◽  
Flow Heat

Researchers are moving forward to provide energy efficient, compact and inexpensive heat exchangers. Main focus is being deployed to the heat exchangers comprising narrow size flow channels such as mesochannels and microchannels for their augmented heat transfer characteristics, compactness and energy efficiency compared to conventional heat exchangers with the same heat exchange duty. Air to water cross-flow heat exchangers are encountered in many engineering applications. While numerous investigations were performed to characterize the heat transfer and fluid flow in mesochannels and microchannels, the literatures examining the air side heat transfer and flow behaviors in the cross-flow mesochannel heat exchangers are inadequate. In the current study air side heat transfer and flow characteristics of cross-flow cooling of air through a multiport slab mesochannel heat exchanger were investigated experimentally. The major components of experimental setup are the closed loop integrated thermal wind tunnel, liquid circulation network with heat add or removal system arrangement, sets of measuring instruments, data acquisition system, and multiport slab mesochannel heat exchanger as the test specimen. The multiport slab mesochannel heat exchanger consists of 15 finned aluminum slabs with 304 mm × 304 mm size frontal area and 100 mm flow length across the direction of air flow. Each slab contains 68 flow channels of 1mm circular diameter. Cold deionized (DI) water at a constant mass flow rate (0.0196 kg/s) was forced to flow through the mesochannels whereas the hot air at different velocities was allowed to pass through the finned passages of the heat exchanger core in cross-flow orientation. The inlet air temperature was changed in three levels (28°C, 33°C and 38°C) while maintaining a constant inlet water temperature of 8° C. The air velocity was varied in four steps (3.5m/s, 5.5m/s, 7.5m/s, and 9.5 m/s) at each temperature level. In the present study heat transfer and fluid flow key parameters such as heat transfer rate (Q˙), number of transfer units (NTU), effectiveness (ε), overall thermal resistance (Rtotal), and the air side Nusselt number (Nua) as well as Reynolds number (Rea) were examined in the region of the air side Reynolds number at the range of 972–2758, with a constant water side Reynolds number of 135. Heat balance performance of the experiment was found to be 4% for all operating conditions. The air side thermal resistance was found to be dominating over the overall thermal resistance ranging from 85% to 91% of the overall thermal resistance. The effect of air side Reynolds number on air side Nusselt number was examined and a general correlation of Nusselt number with Reynolds number was obtained as Nua = 0.3972(Rea)0.3766. The Nusselt number value was found to be higher in comparison with other research works for the corresponding Reynolds number range. The multiport mesochannel flat slab has offered uniform temperature distribution into the core. This uniform temperature distribution leads to higher heat transfer over standalone inline flow tube bank.

scholarly journals Graphing Behaviour of Heat Transfer In Terms of Nusselt and Reynolds

2021 ◽  
Vol 6 (2) ◽  
pp. 41-52
Author(s):  
Mohd Rahimie Md Noor ◽  
Nur Syafiqah Hidayah Mohd Fauzi ◽  
Siti Nur Fadhilah Masrom ◽  
Mohd Azry Abdul Malek ◽  
Muhammad Firdaus Mustapha ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Volume Flow Rate ◽  
Convection Heat Transfer ◽  
Heat Transfer Process ◽  
Two Fluids ◽  
The Relationship

Heat exchangers are tools used to transfer thermal energy between two fluids (liquid or gas) by convection and conduction at different level of temperatures. Heat exchangers are the common equipment and employed in many different applications because of ability to withstand high temperatures and compactness. There are no intermixing or leakage occurred between two fluids during the heat transfer process as fluids are separated by walls of heat exchanger. The main objective of this project is to determine the heat exchanger effectiveness in heat transfer performance. This will be done by investigating the performance of five different angles of heat exchanger which are 150,300, 450, 600 and 750. The effectiveness of heat exchanger depends on the convection heat transfer coefficient of the fluid. Besides that, this project also aims to develop some parameters such as Nusselt number, Reynolds number and Prandtl number for evaluating the heat transfer. It is found that the Nusselt Number at angle of 150 is lower compared to angle of 750. Meanwhile, Reynolds number for angle 150 is higher than angle 750 which means that the type of flow produced by angle 150 is turbulent flow while for 750 angle is laminar flow. Hence, the overall result of this project proved that 150 is the best angle for heat exchanger in chimney because of higher velocity, higher volume flow rate, higher density of gas and higher LMTD. The relationship between Nusselt number and Reynolds number between different angles can be observed by plotting the graph using Maple Software.

scholarly journals Evaluation of selected methods of the heat transfer coefficient determination in fin-and-tube cross-flow heat exchangers

2018 ◽  
Vol 240 ◽  
pp. 02004 ◽  
Author(s):  
Tomasz Bury ◽  
Małgorzata Hanuszkiewicz Drapała
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Transfer Coefficient ◽  
Heat Exchangers ◽  
Cross Flow ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Flow Heat ◽  
The Heat Transfer Coefficient

The work is a part of a thermodynamic analysis of a finned cross-flow heat exchanger of the liquid-gas type. The heat transfer coefficients on the liquid and the gas side and the area of the heat transfer are the main parameters describing such a device. The basic problem in computations of such heat exchangers is determination of the coefficient of the heat transfer from the finned surfaces to the gas. The differences in the heat transfer coefficient local values resulting from the non-uniform flow of mediums through the exchanger complicates the analysis additionally. Six Nusselt number relationships are selected as suitable for the considered heat exchanger, and they are used to calculate the heat transfer coefficient for the air temperature ranging from 10°C to 30°C and for the velocity values ranging from 2 m/s to 20 m/s. In the next step, the gas-side heat transfer coefficient is determined by means of numerical simulations using a numerical model of a repetitive fragment of the heat exchanger under consideration. Finally, the Wilson plot method is also used. The work focuses on an analysis of the in-house HEWES code sensitivity to the method of the heat transfer coefficient determination. The authors believe that the analysis may also be useful for the evaluation of different methods of the heat transfer coefficient computation.

Computational study of Staggered and Double Cross Flow Heat Exchanger

2017 ◽  
Vol 67 (4) ◽  
pp. 396
Author(s):  
Annur Srinivasan Krishnan ◽  
Palanivelu Gowtham
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Fluid Flow ◽  
Heat Exchanger ◽  
Transfer Rate ◽  
Cross Flow ◽  
Flow Reynolds Number ◽  
Flow Heat ◽  
Shell And Tube ◽  
Double Cross

The preliminary findings of a comparative study of heat transfer rate and pressure drop between conventional staggered flow and double cross flow heat exchanger is reported. Excepting for the tube arrangements, the shell and tube dimensions, materials and inlet conditions are retained the same for the two configurations. While in the conventional arrangement, adjacent rows of tubes are normal only to the fluid flow in the shell, in the double cross-flow arrangement, they are normal to both fluid flow direction in the shell as well as to each other. Shell dimensions are 100 cm × 20 cm × 20 cm and tube outside and inside diameters are 1 cm and 0.8 cm. The shell and tube materials are steel and copper. Water and air were considered as tube and shell side fluids respectively, with an overall arrangement of parallel flow. The tube flow Reynolds number was fixed at 2200 and the shell flow Reynolds number was varied from 20 to 120 in the laminar regime and 360 to 600 in the turbulent zone. The study reveals that the proposed configuration gives a maximum increase of about 27 per cent in the heat transfer rate per unit pressure drop over the conventional one.

CFD Analysis of Heat Transfer Characteristics of Helical Coil Heat Exchangers

2015 ◽  
Vol 787 ◽  
pp. 172-176
Author(s):  
R. Maradona ◽  
S. Rajkumar
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Helical Coil ◽  
Cfd Analysis ◽  
Compact Size ◽  
Coil Diameter ◽  
Coil Heat

The applications of heat exchangers are vast and the enhancement of heat transfer and compact size are the key factors for designing the heat exchangers in order to achieve energy savings. In the field of tubular heat exchangers one of the possible ways for reducing the space occupied by the exchanger is by bending tube axis in helical shape. This option is particularly suitable when construction simplicity is needed and the geometry of the place in which the exchanger has to be housed is the cylindrical one. In this paper, an attempt is made to enhance the heat transfer rate without application of any external power. This is achieved by providing the helical tube in tubes. The parameters influencing the nature of flow in a helical coil heat exchanger are the tube geometry namely pitch coil diameter, pitch and tube diameter. CFD analysis is carried out to study these geometry effects on heat transfer and hydraulic characteristics by varying Reynolds number (hot fluid). The CFD results of velocity and temperature distribution in the heat exchanger are used to estimate the Nusselt number and heat transfer coefficient. This helps to arrive at an optimum value of Reynolds number and Nusselt number for the corresponding tube-to-coil diameter ratios.

The Design of Contra-Flow Heat Exchangers

1948 ◽  
Vol 159 (1) ◽  
pp. 351-362 ◽  
Author(s):  
Ernst Schmidt
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Heat Exchange ◽  
Heat Exchangers ◽  
Minimum Weight ◽  
Temperature Drop ◽  
Minimum Volume ◽  
Flow Heat

The problem of contra-flow heat exchangers, for gases at turbulent flow, is treated in a general way, using the analogy between heat transfer and friction. For making this analogy more evident, another non-dimensional heat transfer coefficient is introduced. This number may be used profitably instead of the Nusselt number for describing heat transfer in tubes, and in similar problems. Thus the main dimensions of the apparatus are given in formulae based on the intended heat exchange, the total drop of temperature, the total loss of energy, and the properties of the fluid. It is shown that weight and total volume of the heat exchanger depend on the ratio of temperature drop and loss of energy on both sides of the heat exchanging surface. The conditions of minimum weight and minimum volume are derived.

Thermal Efficiency of the Cross Flow Heat Exchangers

2006 ◽  
Author(s):  
Ahmad Fakheri
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Transfer Rate ◽  
Heat Exchangers ◽  
Transfer Rate ◽  
Cross Flow ◽  
Algebraic Expression ◽  
Counter Flow ◽  
Optimum Heat ◽  
Flow Heat

The heat exchanger efficiency is defined as the ratio of the actual heat transfer in a heat exchanger to the optimum heat transfer rate. The optimum heat transfer rate, qopt, is given by the product of UA and the Arithmetic Mean Temperature Difference, which is the difference between the average temperatures of hot and cold fluids. The actual rate of heat transfer in a heat exchanger is always less than this optimum value, which takes place in an ideal balanced counter flow heat exchanger. It has been shown that for parallel flow, counter flow, and shell and tube heat exchanger the efficiency is only a function of a single nondimensional parameter called Fin Analogy Number. The function defining the efficiency of these heat exchangers is identical to that of a constant area fin with an insulated tip. This paper presents exact expressions for the efficiencies of the different cross flow heat exchangers. It is shown that by generalizing the definition of Fa, very accurate results can be obtained by using the same algebraic expression, or a single algebraic expression can be used to assess the performance of a variety of commonly used heat exchangers.

High Performance Micro-Channel Cross Flow Heat Exchangers

2005 ◽  
Author(s):  
Kevin W. Kelly ◽  
Andrew McCandless ◽  
Christoffe Marques ◽  
Ryan A. Turner ◽  
Shariar Motakef
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
High Performance ◽  
Gas Flow ◽  
Cross Flow ◽  
Micro Channel ◽  
Transfer Coefficients ◽  
Order Of Magnitude ◽  
Flow Heat

The performance of a micro-channel gas-liquid cross flow heat exchanger, manufactured by the LIGA technique is presented. Large heat transfer coefficients are achieved on the gas side by achieving gas-flow passage dimensions as low as 300 microns. Cross flow heat exchanger panels have been produced as large as 20 cm by 15 cm. These panels can be arranged in a variety of ways to produce heat exchangers capable of handling large thermal loads. Experimental results have shown that these heat exchangers are approximately one order of magnitude better, in terms of heat transfer per unit volume, than the commercially available tube-fin heat exchangers with characteristic cross flow channel dimensions that are typically three times larger.

Exergy Transfer Effectiveness on Heat Exchanger

2006 ◽  
Author(s):  
Shuang-Ying Wu ◽  
Xiao-Feng Yuan ◽  
You-Rong Li ◽  
Wen-Zhi Cui ◽  
Liao Quan
Keyword(s):  
Heat Transfer ◽  
Heat Capacity ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Cross Flow ◽  
Counter Flow ◽  
Temperature Heat ◽  
Relevant Variables ◽  
Flow Heat ◽  
Exergy Transfer

In this paper, the concept of exergy transfer effectiveness is put forward firstly and the expressions involving relevant variables for the exergy transfer effectiveness, the heat transfer units number and the ratio of cold and hot fluids heat capacity rate have been derived for the high and low temperature heat exchangers. Taking the parallel flow, counter flow and cross flow heat exchangers as examples, the numerical results of exergy transfer effectiveness are given and the comparison of exergy transfer effectiveness with heat transfer effectiveness is analyzed.

Analisis Perbandingan Jenis Material Penukar Kalor Plat Datar Aliran Silang Untuk Proses Pengeringan Kayu

2021 ◽  
Vol 9 (1) ◽  
pp. 60-71
Author(s):  
Abeth Novria Sonjaya ◽  
Marhaenanto Marhaenanto ◽  
Mokhamad Eka Faiq ◽  
La Ode M Firman
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Flat Plate ◽  
Heat Exchangers ◽  
Fluid Dynamic ◽  
Cross Flow ◽  
Plate Heat ◽  
Dry Air ◽  
Copper Material ◽  
Plate Type

The processed wood industry urgently needs a dryer to improve the quality of its production. One of the important components in a dryer is a heat exchanger. To support a durable heat transfer process, a superior material is needed. The aim of the study was to analyze the effectiveness of the application of cross-flow flat plate heat exchangers to be used in wood dryers and compare the materials used and simulate heat transfer on cross-flow flat plate heat exchangers using Computational Fluid Dynamic simulations. The results showed that there was a variation in the temperature out of dry air and gas on the flat plate heat exchanger and copper material had a better heat delivery by reaching the temperature out of dry air and gas on the flat plate type heat exchanger of successive cross flow and.   overall heat transfer coefficient value and the effectiveness value of the heat exchanger of the heat transfer characteristics that occur with the cross-flow flat plate type heat exchanger in copper material of 251.74725 W/K and 0.25.

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