Offset Fin Heat Exchanger Research Articles

Experimental study on thermal–hydraulic performance of moist air inside flat tube of two kinds of plate-fin heat exchangers

The plate-fin heat exchanger is the core component of the condensing clothes dryer, which has a significant effect on the performance of the dryer. Two types of plate-fin heat exchangers with different fin structures are proposed to improve the performance of condensing dryers, offset-fin heat exchanger and slit-fin heat exchanger. Experimental investigations are conducted to study the thermal–hydraulic performance of moist air inside flat tube. The heat transfer coefficient and pressure drop of the moist air inside flat tube, the heat transfer rate per unit area, latent heat and sensible heat are compared and analyzed under different experimental conditions. The comparison shows that the offset-fin heat exchanger compared with the slit-fin heat exchanger can increase heat transfer rate per unit area by approximately 15%. Moreover, the comprehensive performance improves by 5%, respectively. Finally, correlations for predicting the Nusselt number and Darcy friction factor inside flat tube are proposed. The values deviate within20% and 10%, respectively. The results provide a design guide for applying plate-fin heat exchangers to condensing dryers.

Experimental analysis on drying performance of a condensing clothes dryer with two new plate-fin heat exchangers

In this paper, an off-set fin heat exchanger (OSFHE) and a flying-wing fin heat exchanger (FWFHE) were developed for the condenser of a condensing clothes dryer. They were used to replace the slit fin heat exchanger (SFHE), which is the prototype condenser. Performance parameters, like condensation rate, IEC energy efficiency index (EEI) and specific moisture extraction rate (SMER), were used to assess the dehumidification performance of the heat exchangers and the drying performance of the dryer. Though the fin areas of OSFHE and FWFHE are 20% and 34.2% less than that of SFHE, the experiment results indicated that OSFHE and FWFHE had a faster condensation rate than SFHE during the main drying stage. And the heat exchanger with a faster condensation rate also led to less power consumption of the dryer in most tests. Compared with using SFHE, using OSFHE could decrease the EEI of the dryer by 0.43%. Using FWFHE could reduce the EEI of the dryer by 1.19% and improve the EU energy efficiency class of the dryer from Class C to Class B. Both OSFHE and FWFHE are able to replace SFHE and become a new generation of condensers for clothes dryers.

Prandtl number effect on offset fin heat exchanger performance: predictive model for heat transfer and pressure drop

Laminar models are described which predict heat transfer and pressure drop performance of liquid-cooled offset fin cold plates. These models are developed based on a surface contribution analysis of energy and momentum balances in a unit cell of the offset fin geometry. The Prandtl number was found to have a significant influence on offset fin heat transfer. The Prandtl number effects on heat transfer are categorized into two perspectives: fin perspective and array perspective. The fin perspective Prandtl number effects explain the dependence of the periodic fully developed Nusselt number on Prandtl number. The array perspective is analogous to the thermal entry length perspective in duct flow. Array perspective Prandtl number effects yield higher Nusselt numbers in the entrance region of the offset fin array. The models predict liquid-cooled experimental data within ± 20%, as compared with heat transfer and pressure drop data for Prandtl number ranging from 0.7 to 150 and Reynolds number from 10 to 2000.

Prandtl number effect on offset fin heat exchanger performance: experimental results

This paper describes an experimental apparatus to study heat transfer and pressure drop of liquid-cooled offset fin compact heat exchangers (cold plates). Liquid coolants used in the test are water and polyalphaolefin, for which the Prandtl number ranges from 3 to 150. From the comparison with previous air-cooled models, the liquid-cooled experimental data show that the Prandtl number has a large effect on the Nusselt number of the offset fin geometry. A numerical heat transfer analysis was performed to investigate the surface temperature distribution and uniformity of heat flux in the cold plates. The results demonstrate good agreement with experimental surface temperature measurements. The model results were used to guide data reduction procedures. In particular, significant end effects are predicted. Through experience with the heat transfer model, these end effects were isolated.

Development of an Accordion-type Offset-fin Heat Exchanger for Air-conditioners

Development of an Accordion-type Offset-fin Heat Exchanger for Air-conditioners

Numerical Analysis on Offset Fin Heat Exchanger Including Fin Efficiency.

This paper describes extenive computer-based analytical studies on the offset fin compact heat exchanger, which could assist thermal designers. In order to simulate the fin efficiency affected by the heat conduction from the condenser pipe to the fin, the numerical analysis was applied to a quasi-3-dimensional problem, using the 1 dimensional heat conduction analytical solution as a boundary condition. Using this calculation method, the heat transfer behavior of the offset fin heat exchanger for various fin numbers was examined.

NUMERICAL PREDICTION OF HEAT TRANSFER AND FLUID FLOW IN RECTANGULAR OFFSET-FIN ARRAYS

A computational study of laminar flow and heat transfer in the channels of a rectangular offset-fin heat exchanger is presented. Computations are carried out for the entrance region and continued till the flow becomes periodically fully developed due to the repetitive nature of the geometry. All the heat transfer surfaces are assumed to be at a uniform temperature. A parametric study is made for various values of the aspect ratio and the fin-length parameter. Results show that developing length is about 5-10 modules. Local results are presented to provide a good physical understanding of the flow and heat transfer phenomena. A comparison of the numerical results with the available experimental data is also presented.

An analysis of the effect of plate thickness on laminar flow and heat transfer in interrupted-plate passages

An analysis is presented for the flow and heat transfer in an interrupted-plate passage, which is an idealization of the offset-fin heat exchanger. The plates are considered to be of finite thickness. The effect of the plate thickness on the flow field and heat transfer is investigated through numerical solutions of the governing equations. The flow field is found to be quite complex. It contains recirculation zones behind the trailing edges of the plates, and there occurs significant deflection of the through flow. Whereas this greatly increases the pressure drop required for a given flow rate, the heat transfer from the thick plates does not improve sufficiently. Detailed results are presented for a number of thickness ratios and for a range of the Reynolds number. The overall results are compared with available experimental data.