Eul-Jong Lee

MODELING AND VERIFICATION OF HEAT AND MOISTURE TRANSFER IN AN ENTHALPY EXCHANGER MADE OF PAPER MEMBRANE

In this study, heat and moisture transfer model of an enthalpy exchanger is proposed. With separately measured sorption constant and diffusion coefficient, the model predicts the heat and moisture transfer effectiveness of an enthalpy exchanger. Two sample enthalpy exchangers were tested at a KS condition to verify the model. The model predicts the heat transfer effectiveness within 4%, and the moisture transfer effectiveness within 10%. Pressure drop is predicted within 6%. The spacer fin efficiency for heat transfer was 0.11 to 0.13. The fin efficiency for moisture transfer, however, was negligibly small. For heat transfer, the conduction resistance to total thermal resistance was less than 1%. For moisture transfer, however, membrane resistance was dominant to convective moisture transfer resistance.

Performance Comparison of Heat Transfer Plates for Cooling Tower Air Heater Through Numerical Analysis

Abstract In this study, numerical analysis was performed on three shapes of heat transfer plates (chevron, wave and dimple type), which are currently used as fillers of cooling towers. Results show that heat transfer rates per consumed power were larger for enhanced plates as compared with that of plain plate. Highest heat transfer coefficient was obtained for wave shape followed by chevron and dimple shape. For wave shape, cross corrugations induced significant mixing of fluids, which enhanced the heat transfer. Friction factor yielded a similar trend with the heat transfer coefficient. However, heat transfer rate and pressure drop per sheet was the largest for chevron shape, due to the largest heat transfer area per sheet. Key Words : Heat Transfer Plate, Cooling Tower, Air Heater, Numerical Analysis 본 연구는 2011년도 중소기업 산학연공동기술개발 사업(과제명 : 냉각탑 백연 저감용 판형 플라스틱 공기가열기 개발)의 일환으로 수행되었습니다. 이에 감사드립니다. * Corresponding Author : Nae-Hyun Kim (Incheon University)Tel: +82-32-835-8420 email: knh0001@incheon.ac.krReceived September 19, 2012 Revised (1st October 26, 2012, 2nd November 14, 2012) Accepted December 6, 2012

HEAT AND MOISTURE TRANSFER CHARACTERISTICS OF A PLATE-TYPE ENTHALPY EXCHANGER MADE OF PAPER

In this study, heat and moisture transfer data of an enthalpy exchanger were obtained varying the indoor and outdoor condition systematically. At the same time, equilibrium water content ratios of the membrane were measured. It is shown that equilibrium water content ratio of the membrane increases with the increase of relative humidity. The effect of temperature on equilibrium water content ratio, however, is rather complex. It decreases with the increase of temperature to a certain value, and then increases with further increase of temperature. Moisture transfer effectiveness of the enthalpy exchanger is also affected by relative humidity and temperature. Heat transfer effectiveness, however, is independent of relative humidity and temperature. Moisture transfer effectiveness of the enthalpy exchanger was successfully correlated by equilibrium water content ratio of the membrane.

Numerical Analysis on the Effect of Corrugation Angle on the Performance of Humidifying Element

In this study, the effect of corrugation angle on thermal performance of corrugated plate is numerically investigated with an aim to develop humidifying element. Numerical analysis was conducted for a range of corrugation angle (from 0 o /0 o to 60 o /60 o for equal angle and from 15 o /0 o to 15 o /60 o for unequal angle). Results revealed that both j and f factor increased as corrugation angle increased. Especially, f factor increased significantly at high corrugation angles. j and f factors of unequal angle plates and those of equal angle (obtained by averaging unequal angles) plates were approximately the same. The largest /f 1/3 , which implies the largest heat transfer rate per consumed power, was obtained at 15 o /15 o . Existing correlations under- or over-predicted the present numerical

Thermal Performance of an Enthalpy Exchanger Made of Paper at Different Outdoor Temperatures and Humidities

초록: ,. ·., · · ,...Abstract: An enthalpy exchanger in which heat and moisture transfer occur between the indoor and outdoorair operates at various outdoor conditions. In this study, the effect of the outdoor-air temperature and humidityon the performance of an enthalpy exchanger was experimentally investigated. An apparatus wasspecially-made to accurately measure the incoming and outgoing dry- and wet-bulb air temperatures as well asthe flow rates. Tests were conducted in constant-temperature and constant-humidity chambers at differentoutdoor temperatures and humidities. It is shown that the effectiveness of latent-heat exchange increases as therelative humidity increases; further, this effect exhibited minimal dependence on the absolute humidity.However, the effectiveness of sensible-heat exchange is independent of both temperature and humidity.

Performance of a Plate-Type Cross-Flow Enthalpy Exchanger Made of Paper

The effects of paper properties such as density, air permeability, moisture transmission rate on the thermal performance of plate-type enthalpy exchanger were experimentally investigated. Three enthalpy exchanger samples having different properties were made, and were tested according to the standard test procedure (KS B 6879). Effective efficiencies were defined, which accounted for the air leakage between supply and exhaust streams. Results showed that paper density affected the sensible heat transfer of the samples. Sensible heat transfer increased with density of the paper. It was also shown that moisture transmission rate alone was not a proper indicator for the efficiency of latent heat transfer. Air permeability should also be considered for adequate evaluation of the latent heat transfer. Best performance was obtained for the sample having highest paper density and moderate moisture transmission ratio.Copyright