Sukhyun Kim

Surface Temperature Control of an Insulated Horizontal Pipe under Thermal Radiation Environment

Procedures for estimation of insulation thickness for a horizontal pipe for condensation control or personnel protection has been investigated, parallel to the previous work of a vertical wall case. Parameters include pipe diameter, emissivity, thermal conductivity, and operating temperatures. The results indicated that the surface emissivity plays a very important role in the design of insulation, specially for the case of high temperature application with low Bi. The effect of surface radiation in such case could be up to 65% of the total. Required insulation thickness for the surface temperature control increases as pipe diameter increases and as surface emissivity decreases. Adequate revision of specifications or standards to include newly invented insulation materials with high emissivity has been also suggested.

Analysis on Surface Temperature Control of an Insulated Vertical Wall Under Thermal Radiation Environment

In this study, a rational procedures for estimation of insulation thickness of a vertical wall for condensation control or personnel protection has been investigated. Design parameters are height of the wall, thermal conductivity, emissivity, and operating temperatures. The results indicated that the surface emissivity plays a very important role in the design of insulation for the purpose of surface temperature control, especially in natural convection situation. radiation heat transfer coefficients for some new insulation material surface, such as elastomers, estimated to be more than 90% of the total surface heat transfer coefficient.

An Experimental Study on the Dehumidification Characteristics and the Effectiveness for Operating Conditions of a Desiccant Rotor

An experimental study has been carried out to investigate the dehumidification characteristics for several operating conditions of a compact desiccant rotor. This problem is of particular interest in the design of a desiccant type of dehumidifier. Room temperature, room humidity, regeneration temperature, revolution speed and frontal air velocity of desiccant rotor are varied as operating conditions. The results obtained indicate that dehumidification rate is increased with an increase in the room humidity while dehumidification effectiveness is not changed much. It is also found that the optimal rotor speed and optimal regeneration temperature exist for maximum dehumidification rate and dehumidification effectiveness.

GREENHOUSE GAS EMISSIONS OF A DISTRICT COOLING SYSTEM UTILIZING WASTE HEAT FROM A COGENERATION PLANT

Reduction effect of greenhouse gas emissions from district cooling system by using waste heat from a cogeneration plant has received specific attention from the perspective of national energy and environmental policy, and was studied in this work. For each cooling system of a residential and commercial building, greenhouse gas emissions was estimated and compared to quantify reduction effect on emissions where the heat source of heat-powered cooling system was replaced with a cogeneration waste heat. In addition, to address the problem that the values of waste heat and CEF vary depending on variables such as national or geographical conditions, a general-purpose criterion to measure the utility of substituting a district cooling for a conventional system was suggested.

NONDIMENSIONALIZED ANALYSIS ON SURFACE TEMPERATURE CONTROL OF AN INSULATED VERTICAL WALL

Procedures for estimation of insulation thickness for surface temperature control of low- and high-temperature vertical wall has been investigated. Design logic for insulation thickness was generalized into a simple dimensionless equation. For the case of condensation control, Bi takes a relatively large value of 8, indicating that the insulation material side controls the transport processes, while the case of personnel protection requires a correct understanding of the surface phenomena. Insulation thickness increases drastically with surface emissivity for the former case and vice versa for the latter. Adequate revision of official technical data to include new material and development of finishing material has been also suggested.

Experimental study on Effects of POE oil on R134a Evaporation Heat Transfer in Plate Heat Exchanger

* Dept. of Advanced Fermentation Fusion Science and Technology, Kookmin Univ., ** Dept. of Mechanical Engineering, Graduate School, Kookmin Univ., *** School of Mechanical Systems Engineering, Kookmin Univ. (Received November 12, 2013 ; Revised January 2, 2014 ; Accepted January 3, 2014) - 기호설명 - A : 전열면적 [m

An Experimental Study on Heat Transfer of a Falling Liquid Film in Air Channel Flow

Thermal transport from vertical heated surface to falling liquid film in a channel has been investigated experimentally. Air-flow is introduced into channel to make a counter flow against falling liquid film. This problem is of particular interest in the design of direct contact heat exchange system, such as cooling tower, evaporative cooling system, absorption cooling system, and distillation system. The effects of channel width and air flow rate on the heat transfer to falling liquid film are studied in detail. The results obtained indicate that heat transfer rate is gradually decreased with an increase in the channel width without air flow as well as with air flow in a channel. It is also found that heat transfer rate of air-flow is increased while heat transfer rate of falling liquid film is decreased with an increase in the air flow rate at a given channel width. However, total heat transfer rate from the heated surface is increased as the air flow rate is increased.

Heat Transfer Enhancement by Pulsating Flow in a Plate Heat Exchanger

The heat transfer enhancement by pulsating flow in a plate heat exchanger has been experimentally investigated in this study. The effect of the pulsating flow, such as pulsating frequency and flow rate on the heat transfer as well as pressure drop in a plate heat exchanger has been studied in detail. Reynolds number in cold side of a plate heat exchanger is varied 100∼530 while that of hot side is fixed at 620. The pulsating frequency is considered in the range of 5∼30 Hz. The results of the pulsating flow are also compared with those of steady flow. It is found that the average heat transfer rate as well as pressure drop is increased as flow rate is increased for both steady flow and pulsating flow cases. When pulsating flow is applied to the plate heat exchanger, heat transfer could be substantially increased in particular ranges of pulsating frequency or Strouhal number; St