The Effect of Longitudinal Heat Conduction on Crossflow Heat Exchanger

1978 ◽  
Vol 100 (2) ◽  
pp. 346-351 ◽  
Author(s):  
J. P. Chiou
Keyword(s):  
Heat Conduction ◽  
Heat Exchanger ◽  
Numerical Method ◽  
Thermal Performance ◽  
Fluid Flows ◽  
Operating Conditions ◽  
Wall Structure ◽  
Two Dimensional ◽  
Performance Deterioration

A numerical method to determine the effectiveness of the crossflow heat exchanger, accounting for the effect of the two-dimensional longitudinal heat conduction through the exchanger wall structure in the directions of fluid flows, is presented. The exchanger effectiveness and its deterioration due to the conduction effect have been calculated for various design and operating conditions of the exchanger. The results indicate that the thermal performance deterioration of the exchanger may become significant for some typical applications.

Axial Heat Conduction in Parallel Flow Microchannel Heat Exchangers

2009 ◽  
Author(s):  
B. Mathew ◽  
H. Hegab
Keyword(s):  
Heat Conduction ◽  
Heat Exchanger ◽  
Parallel Flow ◽  
Operating Conditions ◽  
Inlet Temperature ◽  
Microchannel Heat Exchanger ◽  
Cold Fluid ◽  
Axial Heat ◽  
End Wall ◽  
Axial Heat Conduction

This paper deals with the effect of axial heat conduction on the hot and cold fluid effectiveness of a balanced parallel flow microchannel heat exchanger. The ends of wall separating the fluids are subjected to Dirichlet boundary condition. This leads to heat transfer between the microscale heat exchanger and its surroundings and thereby leading to axial heat conduction through the wall separating the fluids. Three one dimensional energy equations were formulated, one for each of the fluids and one for the wall. These equations were solved using finite difference method. The effectiveness of the fluids depends on the NTU, axial heat conduction parameter, and the temperature of the ends of the wall separating the fluids. With decrease in temperature of the end wall at the inlet section of the fluids, while keeping the temperature of the other end wall constant, the effectiveness of the hot and cold fluid increased and decreased, respectively. When the temperature at the ends of the wall separating the heat exchanger is average of the inlet temperature of the fluids then there is no axial heat conduction through the heat exchanger. The effectiveness of a counter flow microchannel heat exchanger is better than that of a parallel flow microchannel heat exchanger subjected to similar operating conditions, i.e. axial heat conduction parameter and end wall temperatures.

Performance Evaluation of Tube-in-Tube Heat Exchanger Using Nanofluids

2015 ◽  
Vol 787 ◽  
pp. 72-76 ◽  
Author(s):  
V. Naveen Prabhu ◽  
M. Suresh
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Heat Transfer Rate ◽  
Thermal Performance ◽  
Transfer Rate ◽  
Flow Characteristics ◽  
Operating Conditions ◽  
Element Analysis ◽  
Tube Heat Exchanger

Nanofluids are fluids containing nanometer-sized particles of metals, oxides, carbides, nitrides, or nanotubes. They exhibit enhanced thermal performance when used in a heat exchanger as heat transfer fluids. Alumina (Al2O3) is the most commonly used nanoparticle due to its enhanced thermal conductivity. The work presented here, deals with numerical simulations performed in a tube-in-tube heat exchanger to study and compare flow characteristics and thermal performance of a tube-in-tube heat exchanger using water and Al2O3/water nanofluid. A local element-by-element analysis utilizing e-NTU method is employed for simulating the heat exchanger. Profiles of hot and cooling fluid temperatures, pressure drop, heat transfer rate along the length of the heat exchanger are studied. Results show that heat exchanger with nanofluid gives improved heat transfer rate when compared with water. However, the pressure drop is more, which puts a limit on the operating conditions.

scholarly journals Thermal Characteristics of High Temperature Naturally Circulating Helium Cooling Loop

2018 ◽  
Vol 68 (1) ◽  
pp. 1-10
Author(s):  
František Dzianik ◽  
Štefan Gužela ◽  
Eva Puškášová
Keyword(s):  
Heat Exchanger ◽  
Thermal Performance ◽  
Fast Reactor ◽  
Natural Circulation ◽  
Thermal Characteristics ◽  
Heat Removal ◽  
Operating Conditions ◽  
Reactor Model ◽  
Decay Heat ◽  
Thermal Calculations

Abstract The paper deals with the process properties in terms of the heat transfer, i.e. the thermal performance of the thermal-process units within a helium loop intended for the testing of the decay heat removal (DHR) from the model of the gas-cooled fast reactor (GFR). The system is characterised by a natural circulation of helium, as a coolant, and assume the steady operating conditions of the circulation. The helium loop consists of four main components: the model of the gas-cooled fast reactor, the model of the heat exchanger for the decay heat removal, hot piping branch and cold piping branch. Using the thermal calculations, the thermal performance of the heat exchanger model and the thermal performance of the gas-cooled fast reactor model are determined. The calculations have been done for several defined operating conditions which correspond to the different helium flow rates within the system.

Some Fundamental Relationships for Tubular Heat Exchanger Thermal Performance

1981 ◽  
Vol 103 (3) ◽  
pp. 573-578 ◽  
Author(s):  
Krishna P. Singh
Keyword(s):  
Heat Exchanger ◽  
Thermal Performance ◽  
Rate Ratio ◽  
Complete Characterization ◽  
Operating Conditions ◽  
State Variables ◽  
Tubular Heat Exchanger ◽  
Temperature Efficiency ◽  
Derivatives Of

Some basic relationships to characterize tubular heat exchanger thermal performance are derived in terms of the well-known state variables. It is shown that the knowledge of η (NTU), R (heat capacity rate ratio), and partial derivatives of the temperature efficiency P with respect to η and R enables complete characterization of the exchanger performance around an operating point. Thus, the exchanger performance can be readily predicted for the so-called “subdesign” conditions. Likewise, additional criteria to compare various exchanger styles for a given range of operating conditions can be developed. Two such criteria are developed in this paper.

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