Abstract
This paper presents an experimental–numerical method for determining heat transfer coefficients in cross-flow heat exchangers with extended heat exchange surfaces. Coefficients in the correlations defining heat transfer on the liquid- and air-side were determined based on experimental data using a non-linear regression method. Correlation coefficients were determined from the condition that the weighted sum of squared liquid and air temperature differences at the heat exchanger outlet, obtained by measurements and those calculated, achieved minimum. Minimum of the sum of the squares was found using the Levenberg–Marquardt method. The uncertainty in estimated parameters was determined using the error propagation rule by Gauss. The outlet temperature of the liquid and air leaving the heat exchanger was calculated using an analytical model of the heat exchanger.
Highlights
Most engineering calculations of heat transfer in heat exchangers use heat transfer coefficients obtained from experimental data [1,2,3]
The theory of different techniques for predicting heat transfer coefficients from single–blow experimental data is simple, the major disadvantage of single blow technique is that its accuracy is very much depending upon how accurately the transient air mass flow rate and transient mass average air temperatures before and after the heat exchanger are measured
The proposed method will be presented in detail on the example of determining correlations for air and water Nusselt numbers for a car radiator, which is a two-row plate fin and tube heat exchanger with two passes
Summary
Most engineering calculations of heat transfer in heat exchangers use heat transfer coefficients obtained from experimental data [1,2,3]. Taler proposed two numerical methods [19,20,21] for determining heat transfer correlations in cross flow compact heat exchangers. The theory of different techniques for predicting heat transfer coefficients from single–blow experimental data is simple, the major disadvantage of single blow technique is that its accuracy is very much depending upon how accurately the transient air mass flow rate and transient mass average air temperatures before and after the heat exchanger are measured. Experimental determination of the local heat transfer coefficient on the surface of a cylinder or tube is very difficult in view of the small difference between the surface temperature of the cylinder which is immersed in cross flow and the liquid, and considering the high circumferential heat flow in the tube or cylinder wall [27]. A mathematical model of the heat exchanger is required that allows calculation of the heat exchanger outlet temperatures of both fluids assuming that mass flow rates and inlet temperatures of both fluids are known
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
