• 유체기계공업학회:학술대회논문집
• /
• 2003.12a
• /
• pp.245-250
• /
• 2003

In order to control indoor air quality and save energy, it is needed to install a suitable ventilation system equipped with heat exchanger for heat recovery. The purpose of this research is to find the performance of paper heat exchanger for exhaust heat recovery, which exchanges latent heat as well as sensible heat. Experimental apparatus comprises heat exchanger model, constant temperature and humidity chamber, fan and measurement systems for temperature, pressure and flow rate. Thermal performance and pressure loss of the paper heat exchanger are measured and compared at various air velocities and outdoor conditions. Experimental results show that paper heat exchanger can recover $50{\sim}70%$ of the enthalpy difference between supply and exhaust air.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
• /
• v.17 no.2
• /
• pp.11-19
• /
• 2021

In this study, combined heat source heat pump system was implemented with 4 single heat source heat pumps each applied with a geothermal source and a water source. Five cases (Case1~Case5) were configured to conduct a performance comparison and analysis of the combined heat source heat pump system. First of all, as a result of analyzing the heat source, the case when 4 ground heat sources were applied (Case1) showed a uniform EST(Entering Source Temperature) distribution throughout the year since it is less affected by outside air compared to the case when 4 water heat sources were applied (Case5). In both winter and summer, the ground heat source maintained higher EST than the water heat source. Therefore, the system with high ratio of geothermal sources is advantageous for heating, and with high ratio of water heat sources is advantageous for cooling.

• Journal of computational fluids engineering
• /
• v.11 no.3 s.34
• /
• pp.8-13
• /
• 2006

The north panel of a geostationary satellite is used as one of the main radiators, on which communication equipment or bus equipment are installed. The thermal control of panel is designed by using embedded heat pipes and surface heat pipes (or external heat pipes) to spread out heat dissipated from equipment all over the radiator evenly and finally to reject the heat to the space through the radiator efficiently. This panel is also divided by several areas based on the operating temperature and dissipation of equipment in order to increase heat rejection capability of radiator. The thermal analysis is carried out for the hot case, Winter Solsitce EOL (End Of Life), in order to validate thermal design of the panel utilized 6 surface heat pipes and 8 embedded heat pipes. The sensitivity studies for the heat pipe failure case and no heat pipe case are performed and compared to its normal state. The heat transport capability of heat pipe is also obtained from these calculations.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.16 no.4
• /
• pp.340-348
• /
• 2004

The air and refrigerant side heat transfer performances are key parameters to improve heat transfer efficiency of the heat exchanger including the fan performance. Design of the fins, treatment of the tube inside, tube diameter and tube array effect heat transfer performance of the heat exchanger. The heat exchanger is used as a condenser at cooling mode and used as an evaporator at heating mode in the heat pump system. The heat pump system uses R410A as the refrigerant. The heat exchangers are consisted with 7 mm diameter tubes with slit-type fins. The study was conducted with variation of arrangement of the refrigerant path and air flow rate and refrigerant pressure drop and heat transfer rate were measured with a code tester. The capacity of the 3 path heat exchanger is more efficient than 2 or 4 path heat exchangers in heating or cooling modes.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.25 no.12
• /
• pp.1711-1720
• /
• 2001

In this study, the heat transfer characteristics of a U-shape heat pipes were investigated. Heat is supplied to the U heat pipe through its middle zone(evaporator), and is released to the environment through its both arms(condensers). Both heat transfer coefficients and heat transport limitations were measured and compared with correlations previously developed for straight type heat pipes. Special concerns were focused to the cases, when each of condensers were submitted to a different cooling conditions, relatively. As a result. the heat transfer limitation of a U-shape heat pipe was found out to be 10∼15% less than the value for a straight heat pipe with an equivalent size.

• Proceedings of the SAREK Conference
• /
• 2008.06a
• /
• pp.901-905
• /
• 2008

This study was conducted to clarify the heat load characteristics and heat and moisture behavior of underground structures. The authors achieved this by carrying out a numerical analysis using simple heat diffusion and simultaneous heat and moisture transfer equations based on measurement data. This paper presents the results of a numerical analysis on the heat load characteristics and heat and moisture behavior of an underground basement and its surrounding ground under a condition of internal heat generation. The authors found it difficult to predict the heat behavior and heat load of the underground basement by simple heat diffusion alone. Accurate prediction of the thermal environment and heat load requires careful consideration of the influences of moisture and precipitation

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.28 no.11
• /
• pp.428-433
• /
• 2016

The fin and tube heat exchanger using a two-port tube has in air-conditioner heat exchanger because heat transfer performance. This study investigates the feasibility of a fin and tube heat exchanger using two-port copper tube by mechanical expansion. The optimum size of the tube-expanding bullet for the heat exchanger using two-port tube was through numerical calculation. The heat exchanger using a two-port tube was fabricated by mechanical expansion, and the heat exchanger performance was evaluated condensation and evaporation experiments. Compared to the heat exchanger of a conventional circular tube, the pressure drop per unit length of the heat exchanger with a two-port tube decreased. Compared to the heat exchanger using a conventional circular tube, the overall heat transfer coefficient of heat exchanger with a two-port tube increased up to 13% in the case of condensation, and up to 25% in the case of evaporation. The two-port tube heat exchanger outperforms conventional heat exchanger for air conditioner with a inner grooved circular tube.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
• /
• v.14 no.1
• /
• pp.1-7
• /
• 2018

A ground source heat pump system should be equipped with devices to measure the generated heating or cooling heat amount in Korea. Generally, the heat measuring devices have been developed to estimate consumed heat amount in residential or commercial buildings from a central air-conditioning system or a district heating system. In this study, two representive heat measuring devices used for buildings were selected, and the accuracy of them were experimentally estimated at the ground source heat pump operating conditions. The obtained heat amounts from the heat measuring devices were deviated within 4.3% comparing with the precise values calculated from an accredited test facility. Even though the accumulated heat amount values of the heat measuring devices had a small difference comparing with the precise values, the temperatures of heat measuring devices showed greatly different values comparing with the precise temperature. Therefore, it is highly recommended to develop the heat measuring devices which is appropriate for the ground source heat pump systems.

• International Journal of Air-Conditioning and Refrigeration
• /
• v.11 no.3
• /
• pp.150-157
• /
• 2003

Local and overall heat transfer characteristics of fin-flat tube heat exchangers with and without vortex generators were investigated. Local heat transfer coefficients were measured with the heat exchanger model using naphthalene sublimation technique. In case of a fin-flat tube heat exchanger without vortex generators, only the horseshoe vortices formed around tubes augment the heat transfer. On the other hand, longitudinal vortices created artificially by vortex generators additionally enhance heat transfer in case of a fin-flat tube heat exchanger with vortex generators. Overall heat transfer coefficients were measured with the prototypes of the fin-flat tube heat exchanger with and without vortex generators in a wind tunnel and results were compared with those of a fin-circular tube heat exchanger with wavy fin. Friction losses for heat exchangers were also measured and compared. The fin-flat tube heat exchanger with vortex generators is found to be more effective than the fin-circular tube heat exchanger with wavy fin.

• Proceedings of the Korean Environmental Sciences Society Conference
• /
• 2003.11a
• /
• pp.165-170
• /
• 2003

A significant surface net heat loss appears around the Kuroshio and the Tsushima Warm Current regions. The area where the surface heat loss occurs should require heat to be supplied by the current to maintain the long-term annual heat balance. Oceanic heat advection in these regions plays an important role in the heat budget. The spatial distribution of the heat supply by the Tsushima Warm Current near the surface was examined by calculating the horizontal heat supply in the surface layer of the East/Japan Sea, directly from historical sea surface temperature and current data. We have also found a simple estimation of the effective vertical scale of heat supply by the current to compensate net heat loss using the heat supplied by the current in the surface 10m layer. The heat supplied by the current for the annual heat balance was large in the Korea/Tsushima Strait and along the Japanese Coast, and was small in the northwestern part of the East/Japan Sea. The amount of heat supplied by the current was large in the northwestern part and small in the southeastern part of the East/Japan Sea. These features suggest that the heat supplied by the Tsushima Warm Current is restricted to near the surface around the northeastern part and extends to a deeper layer around the southeastern part of the East/Japan Sea.