• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.20 no.1
• /
• pp.65-74
• /
• 2008

In Korea, air source heat pump system is less efficient than conventional heat source facilities, such as ground source, river water, because the air temperature in winter season is so low that COP of air source heat pump system drops below 3.0. Therefore, the study on the application of heat pump heating and cooling systems is crucial for the efficient popularization of heat pump. In this work, we present the dynamic analysis of energy consumption for the large resident building by heat resistance-capacitance method. The system simulation of water storage air source heat pump is additionally performed by changing of sizes and locations of the hospital building. The computed results show that energy cost of water storage air source heat pump is low, so it is more economical than absorption chiller & heater.

• Journal of Power System Engineering
• /
• v.21 no.2
• /
• pp.64-69
• /
• 2017

The purpose of this study is to investigate the performance characteristics of seawater cooling system for a fishing vessel. The circulation amount of refrigerant, condensation capacity, evaporation capacity, compression work and coefficient of performance(COP) were analyzed as the heat source temperature changed. The experimental setup consisted of an open-type compressor, a shell&tube type condenser, an evaporator and an expansion valve. The heat source was controlled by a constant temperature chamber. The main results of this study are summarized as follows. The condensation capacity increased with increasing heat source temperature, and it was confirmed that the effect of circulating amount of refrigerant was dominant. The amount of heat for vaporization was almost constant even though the temperature of the heat source increased. On the other hand, the compression power was increased. This is because the compression ratio increases as the condensation pressure, the enthalpy difference between inlet and outlet, the amount of circulating refrigerant increases. The performance coefficient of this system showed a tendency decreasing with increasing heat source temperature. Therefore, the basic data of the seawater cooling system for the maintenance of the catch line of the shore fishing boats was acquired through this study, and it is considered that it will be sufficient for the actual design.

• Proceedings of the SAREK Conference
• /
• 2007.11a
• /
• pp.564-569
• /
• 2007

This study describes thermal performance of solar cooling and hot water for demonstration system with ETSC(Evacuated tubular solar collector) installed at Seo-gu art center of Kwangju. For demonstration study, a reading room with about 350㎡ was heated and cooled with the solar system. The system was consisted of ETSCs, storage tank, hot water supply tank, subsidiary boiler, subsidiary tank, absorption chiller, chiller storage tank, and cooling tower. The results of the experimental study indicated that the total solar energy gain as daily performance on a sunny day (August 25, 2007) with total daily radiation of $606\;W/m^2$ was 671 kWh, the collecting efficiency of 55%. In the case of supplies to heat source more than $83^{\circ}C$, cooling time operated by solar was driven 8.8 hours, cooling energy generated by solar system was 179 kWh and the solar cooling fraction was 79.2%, and hot water supplied with surplus heat source by the solar system was 201 kWh.

• Transactions of the Korean hydrogen and new energy society
• /
• v.31 no.2
• /
• pp.242-249
• /
• 2020

The Kalina cycle (KC) is considered as one of the most efficient systems for recovery of low grade heat. Recently, Kalina based power and cooling cogeneration cycles (KPCCCs) have been suggested and attracted much attention. This paper presents an energy and exergy analysis of a recently suggested KPCCC with flexible loads. The cycle consists of a KC (KCS-11) and an aqua-ammonia absorption refrigeration cycle. By adjusting the splitting ratios, the cycle can be operated with four modes of pure Kalina cycle, pure absorption cooling cycle, Kalina-cooling parallel cycle, and Kalina-cooling series cycle. The effects of system variables and the operating modes on the energetic and exergetic performances of the system are parametrically investigated. Results show that the system has great potential for efficient utilization of low-grade heat source by adjusting loads of power and cooling.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
• /
• v.17 no.4
• /
• pp.59-67
• /
• 2021

In this study, the performance of the single heat source system and the hybrid system was comparatively analyzed. Case 1 is a ground heat source system, and Case 2 is a water heat source system. Case 3, a hybrid system, reduced the capacity of the ground heat source and applied a water heat source as an auxiliary heat source, and Case 4 was composed of a system that applied a water heat source as an auxiliary heat source to the ground heat source system. As a result of the simulation, in case 3, energy consumption was reduced by up to 2.67% compared to ground sources for cooling. In Case 4, COP was improved by up to 10.02% compared to ground sources during cooling, and EST was calculated to be 2.42℃ lower. During heating, 0.83% was improved compared to the water heat source. At this time, the EST was calculated to be 2.25℃ higher than the water heat source.

• Journal of the Korean housing association
• /
• v.15 no.2
• /
• pp.107-115
• /
• 2004

The objective of this study is to show the system Integrations and control method for operation of the Radiant Floor Cooling. The systems for radiant floor cooling system consist of only using the radiant floor cooling and the radiant floor cooling integrated with a dehumidification system. And the study is suggested control method with composed radiant floor cooling system through simulations. Radiant floor cooling systems compose of four main parts: an existing radiant heating panel, manifold, cooling source and controller, and sensors. If dehumidifying or supplementary cooling is needed, additional equipments such as PAC and AHU are needed. Simulation results show that control method only using radiant floor cooling system can prevent condensation and set room air temperature with the exception of hot and humid periods and control method using the radiant floor cooling integrated with a dehumidification system is comfort thermal environments and can reduce the cooling load quickly, moreover, show comfort control method to meet various cooling operation situations.

• The Journal of the Acoustical Society of Korea
• /
• v.22 no.3
• /
• pp.217-223
• /
• 2003

A novel cooling method induced by acoustic streaming generated by ultrasonic vibration at 30㎑ is presented. Ultrasonic vibration is obtained by piezoelectric devices and the maximum vibration amplitude of 50 m is achieved by including a horn, mechanical vibration amplifier in the system and making the complete system resonate. To investigate the enhancement of heat transfer capability of acoustic streaming, the temperature variations of heat source and air in the vicinity of heat source are measured in real-time. It is observed that acoustic streaming is instantly induced by ultrasonic vibration, resulting in the significant temperature drop due to the bulk air flow caused by acoustic streaming. In addition, it is observed that the cooling effect on the heat source is maximized when the gap between the ultrasonic vibrator and heat source coincides with the multiples of half-wavelength of the ultrasonic wave. This fact results from the resonance of the sound wave. The theoretical analysis of the dependence on the gap is also accomplished and verified by experiment. The advantage of the proposed cooling method by acoustic streaming is noise-free due to the ultrasonic vibration and maintenance-free because of the absence of moving parts. Moreover. This cooling method can be utilized to the nano and micro-electro mechanical systems, where the fan-based conventional cooling method can not be employed.

• Proceedings of the SAREK Conference
• /
• 2008.06a
• /
• pp.294-298
• /
• 2008

The major threats that human being is facing nowadays are the Climate change, depletion of the fossil fuels at a rapid rate and energy costs. A significant portion of world energy consumption is consumed by domestic heating and cooling. And heat pumps, due to their higher utilization efficiencies as compared to conventional heating and cooling systems, offer an attractive solution to this problem. Among the types of heat pumps, the Geothermal heat pump or Ground-source heat pump is a highly efficient, renewable energy technology for space heating and cooling. The Ground-source heat pump uses the Earth as a heat sink in the summer and a heat source in the winter. And the Earth, having a relatively constant temperature, warmer than the air in winter and cooler than the air in summer, offers an excellent heat source in winter and heat sink in summer.. This paper will discuss an overview of the types of heat pumps, its operation, benefits of using geothermal heat pumps, soil characteristics, and overview of some experimental works. Finally it will briefly discuss the opportunity of using these energy efficient systems (EES) in the HVAC market of South Korea.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.21 no.3
• /
• pp.303-313
• /
• 2023

Spent fuels (SFs) are stored in a storage pool after discharge from nuclear power plants. They can be transferred to for the further processes such as dry storage sites, processing plants, or disposal sites. One of important measures of SF is the burnup. Since the radioactivity of SF is strongly dependent on its burnup, the burnup of SF should be well estimated for the safe management, storage, and final disposal. Published papers about the methodology for the burnup estimation from the known activities of important radioactive sources are somewhat rare. In this study, we analyzed the dependency of the burnup on the important radiation source activities using ORIGEN-ARP, and suggested simple correlations that relate the burnup and the important source activities directly. A burnup estimation equation is suggested for PWR fuels relating burnup with total neutron source intensity (TNSI), initial enrichment, and cooling time. And three burnup estimation equations for major gamma sources, ¹³⁷Cs, ¹³⁴Cs, and ¹⁵⁴Eu are also suggested.

• Journal of the Korean Society of Industry Convergence
• /
• v.12 no.1
• /
• pp.11-18
• /
• 2009

The air flow and heat transfer characteristics of an air jet impinging on a pedestal heat source has been investigated numerically to examine the effects of geometric parameters such as nozzle-to-pedestal spacing, nozzle diameter and pedestal size. Also, the parameters of Reynolds number, air jet power, supplied heat and thermal conductivity of pedestal have been studied to reveal how these affect the average Nusselt number. Hence, a two-dimensional turbulent model has been developed and adopted to simulate the fluid flow and heat transfer phenomena numerically. The results obtained from the model show that the nozzle-to-pedestal spacing, relative size of nozzle to pedestal and Reynolds number of air jet have a significant influence on the cooling characteristics of heated pedestal. Furthermore, some useful guidelines could be given to the application of cooling the heated pedestal.