• Title/Summary/Keyword: Direct Contact Heat Exchange

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A Study on the Heat Release Characteristics of Gel Type Micro Size Latent Heat Storage Material Slurry with Direct Contact Heat Exchange Method (겔 상태의 미세 잠열 축열재 혼합수의 기액직접접촉식 열교환법에 의한 방열 특성)

  • 김명준
    • Journal of Advanced Marine Engineering and Technology
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    • v.28 no.4
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    • pp.618-623
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    • 2004
  • This paper has dealt with the heat storage characteristics of gel type micro size latent heat storage material slurry. The heat release operation to the gel type micro size latent heat storage material slurry was carried out using hot air bubbles by direct contact heat exchange. This experiment was carried out using phase change material of n-paraffin so the heat release amount is higher than cold water system. The parameters of this experiment were concentration of latent heat phase change material, height of heat release bath and inlet velocity of hot air. The main results obtained are as follows : (1) The effect of concentration of latent heat phase change material dispersed with water is very affective to the direct contact heat exchange between hot air and gel type micro size latent heat storage material slurry. (2) It is clarified that the most effective concentration of latent heat phase change material dispersed with water exists around 20mass% at this type of direct heat exchange model experiment.

Air handling unit utilizing water/air direct contact heat exchanger with mesh (공기조화기내 메쉬삽입 물-공기 직접접촉의 열전달 특성 연구)

  • Jeon, Yong-Han;Mun, Myeong-Hun;Kim, Jong-Yoon;Kim, Nam-Jin;Seo, Tae-Boem;Kim, Chong-Bo
    • Proceedings of the SAREK Conference
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    • 2008.06a
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    • pp.1161-1166
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    • 2008
  • The objective of this research was to investigate the enhancement of heat transfer by mesh in water/air direct contact air conditioning system. Mesh is inserted as a turbulent promoter in front of the water injection nozzle. The heat transfer characteristics with and without mesh and the effect of the number of inserted mesh and mesh porosity size have been studied experimentally. Inserted mesh improves heat transfer efficiency compared to non-inserted mesh system and heat transfer efficiency increased as the number of mesh is increased. Meanwhile, heat transfer efficiency decreased as the porosity of the mesh is increased. With inserted mesh, inlet and outlet temperature difference of air increased more than 50%. Heat exchange time of water/air to reach the 100% humidity decreased less than 30%. This result shows inserted mesh can enhance the performance of the water/air direct contact air conditioning system.

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Air Handling Unit Utilizing Water/Air Direct Contact Heat Exchanger with Mesh (공기조화기내 메쉬삽입 물-공기 직접접촉의 열전달 특성 연구)

  • Jeon, Yong-Han;Kim, Jong-Yoon;Kim, Nam-Jin;Seo, Tae-Boem;Kim, Chong-Bo
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.20 no.1
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    • pp.75-80
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    • 2008
  • The objective of this research was to investigate the enhancement of heat transfer by mesh in water/air direct contact air conditioning system. Mesh is inserted as a turbulent promoter in front of the water injection nozzle. The heat transfer characteristics with and without mesh and the effect of the number of inserted mesh and mesh porosity size have been studied experimentally. Inserted mesh improves heat transfer efficiency compared to non~inserted mesh system and heat transfer efficiency increased as the number of mesh is increased. Meanwhile, heat transfer efficiency decreased as the porosity of the mesh is increased. With inserted mesh, inlet and outlet temperature difference of air increased more than 50%. Heat exchange time of water/air to reach the 100% humidity decreased less than 30%. This result shows inserted mesh can enhance the performance of the water/air direct contact air conditioning system.

Development and Research of Thermal Management Equipment for Efficiency Enhancement of PEMFC Systems (PEMFC 시스템 효율 향상을 위한 열 관리 설비 개발 및 연구)

  • JAEHWAN KIM;JISEUNG LEE;INSEAK KANG;HYUNCHUL JU
    • Transactions of the Korean hydrogen and new energy society
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    • v.35 no.2
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    • pp.205-215
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    • 2024
  • This study introduced a direct contact heat exchanger to enhance the efficiency of polymer electrolyte membrane fuel cells (PEMFCs) systems. According to previous research, 28% of the operating costs of fuel cell systems are attributed to heat exchanger devices, prompting the design of a direct contact heat exchanger to address this issue. Optimal configurations were determined through computational fluid dynamics analysis and experimental device fabrication, and the enhanced heat exchange performance of the heat exchanger was experimentally confirmed. Through this, the contribution of the direct contact heat exchanger to the heat management and efficiency enhancement of PEMFC systems was established.

Study on the Ethanol Recovery Process using Dircet Contact Heat Exchange (고온의 기포접촉에 의한 에탄올 회수공정에 관한 연구)

  • Lee, Won-Young;Yeo, Sang-Do;Choi, Yong-Hee
    • Korean Journal of Food Science and Technology
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    • v.27 no.2
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    • pp.176-180
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    • 1995
  • Direct contact heat exchange (DCHE) method has been employed to investigate the separation of ethanol from dilute aqueous solutions. Bubbles at high temperature were dispersed into a continuous liquid phase, generating temperature gradient in air-liquid interface, which causes heat and mass transfer accordingly. The experiments were performed in the ranges of jet regime air flow. The air-water stripping coefficient increased $5{\sim}10,\;and\;1{\sim}1.5$ times as temperature and air flow rate increased, respectively. The recovery ratio based on the initial ethanol concentration reached into 80% at the air flow rate of 84.88 m/min. The initial ethanol concentration showed little effect on the stripping coefficient and the recovery ratio.

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A Study on the Heat Recovery from Boiler Exhaust Gas with Multi-stage Water-fluidized-bed Heat Exchanger (다단 물유동층 열교환기에 의한 보일러 배가스의 폐열 회수 성능에 관한 연구)

  • Kim, Dae-Gi;Park, Sang-Il;Kim, Han-Deok
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.25 no.12
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    • pp.1776-1783
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    • 2001
  • Heat recovery from boiler exhaust gas with multi-stage water-fluidized-bed heat exchanger is analyzed in this study. The recovered energy here is not only sensible heat but also latent heat contained in the exhaust gas. In this system direct contact heat transfer occurs while exhaust gas passes through water bed and the thermal energy recovered this way is again delivered to the water circulating through heat exchanging pipes within the bed. Thus the thermal energy of exhaust gas can be recovered as a clean hot water. A computer program developed in this study can predict the heat transfer performance of the system. The results of experiments performed in this study agree well with the calculated ones. The heat and mass transfer coefficients can be fecund through these experiments. The performance increases as the number of stage increases. However at large number of stages the increasing rate becomes very low.

An Experimental study on heat transfer of a falling liquid film in air channel flow (채널내 공기유동이 있는 유하액막의 열전달특성에 관한 실험적 연구)

  • Oh, Dong-Eun;Kang, Byung-Ha;Kim, Suk-Hyun
    • Proceedings of the KSME Conference
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    • 2007.05b
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    • pp.2291-2296
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    • 2007
  • 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 form the heated surface is increased as the air flow rate is increased.

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An Experimental Study on Heat Transfer of a Falling Liquid Film in Air Channel Flow (채널내 공기유동이 있는 유하액막의 열전달특성에 관한 실험적 연구)

  • Oh, Dong-Eun;Kang, Byung-Ha;Kim, Suk-Hyun;Lee, Dae-Young
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.32 no.5
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    • pp.335-341
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    • 2008
  • 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.

Performance Enhancement of Solar-Driven Steam Generator by Local Wettability Control (태양열 활용 증발기의 성능 향상을 위한 국소적 젖음성 제어에 관한 실험적 연구)

  • Choi, Jinwook;Seo, Yongwon;Mo, Hyeong-Uk;Kim, Seolha
    • Korean Chemical Engineering Research
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    • v.60 no.2
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    • pp.255-259
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    • 2022
  • Solar membrane steam generation is a very promising technology that can harvest purified water from seawater or wastewater during the current danger of running out of pure water. However, solar Membrane steam generation had direct contact with water, making it difficult to increase the efficient amount of evaporation. Here, we propose solar membrane steam generator composed of polydimethylsiloxane (PDMS) and graphene oxide (GO) and improved evaporation through wettability control in part throughout the water-absorbing membrane. Wettability control has shown significant improvements in thermal localization and temperature rise in the area of heat exchange with sunlight. The evaporator has an evaporation rate of 1.54 kg m-2 h-1 under 1 sun irradiation. The results showed that Solar membrane steam evaporation can effectively harvest pure water through an increase in evaporation.