In this paper, a heat exchange system using cooling dehumidification and mixing process was proposed as an experimental study for a white smoke reduction heat exchanger system under winter condition. The white smoke reduction heat exchange system is divided into an EA part, SA part, W part and mixing zone. For the operating conditions, three types (Cases 1, 2, and 3) were selected depending on whether EA fan, SA fan, and A-W heat exchanger were operated. In addition, in order to visualize the white smoke exhausted from the mixing zone, it was photographed using CCTV. In order to investigate the performance of the white smoke reduction heat exchange system, the temperature reduction rate and absolute humidity reduction rate of EA and the heat recovery rate of W were calculated. The temperature change of EA and SA according to operating conditions was most effective in Case 3, and the temperature and absolute humidity at the outlet of the mixing zone were greatly reduced. From the results of the white smoke visualization, it was confirmed that the white smoke generation mechanism was different depending on the operating conditions, and the amount of white smoke generation was greatly reduced.

One simple way of increasing the heat transfer for a fin-and-tube heat exchanger is to increase the fin surface area. In this study, a series of tests were conducted on wide slit fin heat exchangers having an increased fin area (Pl/Pt = 0.87), and the results were compared with those of standard slit fin heat exchangers (Pl/Pt = 0.6). Thermal performances of wide silt-finned samples were superior to those of standard slit fin samples. For one row configuration, the j factor of the wide slit fin sample was 11% larger, and the f factor was 33 % smaller than those of the standard slit fin sample. The difference decreased as the number of tube row increased, although wide slit fin sample always yielded superior performance, The reason was attributed to the many narrower slits formed on the wide fin sample. Furthermore, the effect of fin pitch on j and f factor was not significant, and j factor decreased with the increase of the number of tube row.

The effect of inclination angle and attack angle on heat transfer enhancement of trapezoidal vortex generator was numerically investigated. The commercial package STAR-CCM+ was utilized to analyze the heat transfer and flow characteristics with various inclination and attack angle of vortex generator. The result shows that the optimum inclination angles are α =30°~40° in terms of the heat transfer and pressure drop. At more than 40° of inclination angle, the transverse vortex is dominant, so that the pressure drop is severe and the heat transfer is reduced. As the attack angle is increased, the transverse vortex is reduced, so that the pressure drop is improved. The optimum attack angle is β =30° because the heat transfer performance is maintained. However, more than 30° of attack angle, the heat transfer is decreasing.

In the present study, the white reduction system was designed and manufactured to evaluate the performance of a heat exchange system using a wave heat exchanger. The reducing effect of white smoke and the amount of heat recovered from cooling water were investigated experimentally using the cooling and dehumidifying method. The white smoke reduction system consists of two parts; the generating part and the reducing part of white smoke. Experimental conditions on EA(exhaust air) and SW(supply water) were fixed. And the outlet temperature and absolute humidity of EA were measured according to inlet velocity of SA(supply air). The outlet temperatures and absolute humidities of EA gradually decreased as inlet velocities of SA increased. From the experimental results, we can see that the absolute humidity reduction rate of EA was max. 84%, and the heat recovery rate of SW was max. 42%.

In this study, the performance of a small - sized wave heat exchanger to be applied to the white smoke reduction system was experimentally confirmed. The heat transfer rate, drain and pressure drop were measured according to the air flow rate, water flow rate and relative humidity change of the wave heat exchanger for two kinds of pitch numbers. A constant temperature and humidity calorimeter and a constant temperature water bath were used to measure the performance of the wave heat exchanger. The heat transfer rate and drain increased gradually with changes of water flow rate. Case 2 showed more than 50% higher heat transfer rate and drain than Case 1. The increase of air heat transfer rate and drain according to air flow rate was greatly increased when the number of pitches was the same or increased, unlike the result of water flow rate change. In the temperature visualization using a thermal imaging camera, it can be seen that as the water flow rate and the number of pitches increase, the heat transfer becomes more effective in Case 2.

Numerical models of composite floor systems with various thickness of phase change material and sizes of circular spacers were developed based on finite element analysis. In order to perform a heat transfer analysis, thermal properties of steels were determined and those of phase change material were estimated from experiment results. In addition, the thermal insulation performance of composite floor systems with respect to different thickness of phase change material and sizes of circular spacers was predicted. To verify the validity of analysis, analysis results were compared with vertical furnace fire test results of equivalent conditions. As a result, available thicknesses of phase change material and sizes of circular spacers were proposed to satisfy the thermal insulation criteria of Korean Standards.