Experimental Study of the Air Side Performance of Fin-and-Tube Heat Exchanger with Different Fin Material in Dehumidifying Conditions

Abstract

Under dehumidifying conditions, the condensed water will directly affect the heat transfer and resistance characteristics of a fin-and-tube heat exchanger. The geometrical form of condensed water on fin surfaces of three different fin materials (i.e., copper fin, aluminum fin, and aluminum fin with hydrophilic layer) in a fin-and-circular-tube heat exchanger was experimentally studied in this paper. The effect of the three different fin materials on heat transfer and friction performance of the heat exchanger was researched, too. The results show that the condensation state on the surface of copper fin and aluminum fin are dropwise condensation. The condensation state on the surface of the aluminum fin with the hydrophilic layer is film condensation. For the three different material fins, increasing the air velocity (ua,in) and relative humidity (RHin) of the inlet air can enhance the heat transfer of the heat exchanger. Friction factor (f) of the three different material fins decreases with the increase of ua,in, however, increases with the increase of RHin. At the same ua,in or RHin, Nusselt number (Nu) of the copper fin heat exchanger is the largest and Nu of the aluminum fin with hydrophilic layer is the smallest, f of the aluminum fin heat exchanger is the largest and f of the aluminum fin with hydrophilic layer is the smallest. Under the identical pumping power constrain, the comprehensive heat transfer performance of the copper fin heat exchanger is the best for the studied cases.

Numerical Study on Non-Uniform Temperature Distribution and Thermal Performance of Plate Heat Exchanger

“…As the inlet temperature of the cold side decreased from 303.15 K to 283.15 K, the effectiveness increased from 0.576 to 0.597. Therefore, the stratified volume of the cold side decreases from 3.73 cm 3 to 3.64 cm 3 , and the stratified volume of the hot side also slightly decreases from 6.13 cm 3 to 5.97 cm 3 . Moreover, the difference between the average temperature and the outlet temperature of the stratified region at the cold and hot sides decreased from 1.18 K to 0.55 K and from 1.94 K to 0.92 K. The size of the stratified region varies depending on the operating conditions of the plate heat exchanger, which affects the non-uniformity of the outlet temperature.…”

“…Figure 9 shows the volume of the stratified region and the average temperature difference at the outlet, and the volume of the stratified region according to the change in availability. As the heat exchanger effectiveness increased from 0.436 to 0.615 due to an increase in the mass flow rate of the cold side, the stratified volume of the cold side-channel decreased from 4.056 cm 3 to 3.67 cm 3 , while the stratified volume of the hot side-channel increased from 5.61 cm 3 to 6.02 cm 3 . In addition, the average temperature of the stratified region and the temperature difference at the outlet decreased from 1.21 K to 0.61 K on the cold side.…”

“…The increase in effectiveness in the heat exchanger reduces the stratified volume for each channel. As the inlet temperature of the cold side decreases from 303.15 K to 283.15 K, the effectiveness increases from 0.576 to 0.597, and the stratified volume of the cold side changes from 3.73 cm 3 to 3.64 cm 3 . The stratified volume of the hot side also decreased slightly from 6.13 cm 3 to 5.97 cm 3 .…”

“…As the inlet temperature of the cold side decreases from 303.15 K to 283.15 K, the effectiveness increases from 0.576 to 0.597, and the stratified volume of the cold side changes from 3.73 cm 3 to 3.64 cm 3 . The stratified volume of the hot side also decreased slightly from 6.13 cm 3 to 5.97 cm 3 . As the inlet temperature of the cold side decreased from 303.15 K to 283.15 K, the effectiveness increased from 0.576 to 0.597.…”

“…Recently, as energy reduction and greenhouse gas emission regulations are being strengthened worldwide, a lot of efforts such as wettability improvement effect [1,2], optimization of fin material, shape, arrangement [3][4][5], application of the nanofluid [6,7], using the nozzle for jet impingement heat transfer [8,9], using porous media [10], optimization of the flow distribution [11][12][13][14] are being implemented to improve the efficiency of heat exchangers. Payambarpour et al [1,2] numerically confirmed the decrease in thermal efficiency as the locally wetted surface increased in the plate tube heat exchanger and noted that the concentrated pattern had higher thermal efficiency in the wetted region than the localized pattern.…”