Conduction Heating of Objects of Simple Shape in a Fluid With Finite Heat Capacity

1988 ◽  
Vol 110 (3) ◽  
pp. 551-553 ◽  
Author(s):  
Q. T. Pham
Keyword(s):  
Heat Capacity ◽  
Analytical Solution ◽  
Approximate Method ◽  
Correction Factor ◽  
Temperature Difference ◽  
Fluid Temperature ◽  
Equivalent Temperature ◽  
Simple Shape ◽  
Mean Temperature ◽  
Simple Regression

A unified analytical solution and an approximate method are presented for calculating the time to cool or heat an object of simple shape to a given mean temperature, using a fluid with finite heat capacity in batch, parallel-flow, or counterflow modes. In the approximate method, an equivalent constant fluid temperature is calculated, which would give the same log-mean temperature difference. The cooling time at this equivalent temperature is found by conventional methods, then multiplied by a correction factor calculated from a simple regression equation.

Mean Temperature Difference Charts for Air Coolers

1983 ◽  
Vol 105 (3) ◽  
pp. 592-597 ◽  
Author(s):  
A. Pignotti ◽  
G. O. Cordero
Keyword(s):  
Heat Transfer ◽  
Heat Capacity ◽  
Temperature Difference ◽  
Optimization Technique ◽  
Independent Variables ◽  
Mean Temperature ◽  
Air Cooler ◽  
The Mean ◽  
The One ◽  
Water Ratio

Computer generated graphs are presented for the mean temperature difference in typical air cooler configurations, covering the combinations of numbers of passes and rows per pass of industrial interest. Two sets of independent variables are included in the graphs: the conventional one (heat capacity water ratio and cold fluid effectiveness), and the one required in an optimization technique of widespread use (hot fluid effectiveness and the number of heat transfer units). Flow arrangements with side-by-side and over-and-under passes, frequently found in actual practice, are discussed through examples.

Heat Exchanger Efficiency

2006 ◽  
Vol 129 (9) ◽  
pp. 1268-1276 ◽  
Author(s):  
Ahmad Fakheri
Keyword(s):  
Heat Capacity ◽  
Heat Exchanger ◽  
Temperature Difference ◽  
Heat Exchangers ◽  
Second Law Of Thermodynamics ◽  
Arithmetic Mean ◽  
Inlet Temperature ◽  
Mean Temperature ◽  
Flow Heat ◽  
The Ideal

This paper provides the solution to the problem of defining thermal efficiency for heat exchangers based on the second law of thermodynamics. It is shown that corresponding to each actual heat exchanger, there is an ideal heat exchanger that is a balanced counter-flow heat exchanger. The ideal heat exchanger has the same UA, the same arithmetic mean temperature difference, and the same cold to hot fluid inlet temperature ratio. The ideal heat exchanger’s heat capacity rates are equal to the minimum heat capacity rate of the actual heat exchanger. The ideal heat exchanger transfers the maximum amount of heat, equal to the product of UA and arithmetic mean temperature difference, and generates the minimum amount of entropy, making it the most efficient and least irreversible heat exchanger. The heat exchanger efficiency is defined as the ratio of the heat transferred in the actual heat exchanger to the heat that would be transferred in the ideal heat exchanger. The concept of heat exchanger efficiency provides a new way for the design and analysis of heat exchangers and heat exchanger networks.

scholarly journals Analytical solution for the effect of increasing CO2 on global mean temperature

Nature ◽  
1985 ◽  
Vol 316 (6029) ◽  
pp. 657-657 ◽  
Author(s):  
T. M. L. Wigley ◽  
M. E. Schlesinger
Keyword(s):  
Analytical Solution ◽  
Global Mean Temperature ◽  
Mean Temperature ◽  
Global Mean
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