A Simplified Model for the Prediction of the Thermal Performance for Cross Flow Air Cooled Heat Exchangers with a New Air Side Thermal Correlation

Hussain Tarrad, Ali; Abdul Wahed, Athe; Dhamia,; Saad Khudor, A

	A Simplified Model for the Prediction of the Thermal Performance for Cross Flow Air Cooled Heat Exchangers with a New Air Side Thermal Correlation
Journal of Engineering and Sustainable Development
Article 1, Volume 12, Issue 3, 2008, Pages 88-119
Authors
Ali Hussain Tarrad; athe Abdul Wahed; ; a Saad Khudor
Abstract
This investigation deals with the performance prediction of the cross flow air cooled heat exchangers. Experimental and theoretical studies were conducted to perform the optimization of the thermal design of the heat exchanger. The experimental work was carried out by two different types and sizes of finned tube air cooled heat exchangers. An experimental rig was built for this object which provides hot water at the range of (40 to 70) Cº with water circulating rate of (200 to 1800) l/hr at absolute pressure of (2) bar. A centrifugal fan was installed as a major part of the experimental rig to provide atmospheric air with volumetric flow rate of (1250 and 2500) cfm. The performance parameters measured in the experimental work were flow rates and temperature at the entering and leaving sides of the process and service fluids passing through the heat exchanger. Further, the water side operating pressure at the inlet and exit ports, and the wet bulb temperature of air on both sides of heat exchanger have been measured as well. The entering air dry bulb and wet bulb temperatures were in the range (16 to 24) Cº and (13 to 20) Cº respectively. The air leaving dry bulb and wet bulb temperatures were (23 to 40) Cº and (15 to 26) Cº respectively. In the theoretical part of this work, a simplified correlation for the air side heat transfer coefficient for the cross flow heat exchangers was suggested in the present work. This formula was based on the dimensionless groups of the Buckingham-pi theorem. It was incorporated in the general formula for the overall heat transfer coefficient for the prediction of the heat exchanger performance. The discrepancy between the predicted and experimental values of the overall heat transfer coefficient and heat duty were within (2%) and (4%) respectively for both of the tested tube banks. The results of the present correlation of the air side heat transfer coefficient revealed a good agreement with that of the well known McQuiston method

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