시설원예를 위한 수평형 지열 히트펌프의 냉방성능 해석

Cooling Performance of Horizontal Type Geothermal Heat Pump System for Protected Horticulture

  • 유영선 (농업공학연구소 시설자원공학과) ;
  • 강연구 (농업공학연구소 시설자원공학과) ;
  • 강금춘 (농업공학연구소 시설자원공학과) ;
  • 김영중 (농업공학연구소 시설자원공학과) ;
  • 백이 (원예연구소 부산원예시험장 시설구조자재연구실)
  • Ryou, Young-Sun (Agricultural Facilities and Resources Engineering Division, NIAE, RDA) ;
  • Kang, Youn-Ku (Agricultural Facilities and Resources Engineering Division, NIAE, RDA) ;
  • Kang, Geum-Chun (Agricultural Facilities and Resources Engineering Division, NIAE, RDA) ;
  • Kim, Young-Joong (Agricultural Facilities and Resources Engineering Division, NIAE, RDA) ;
  • Paek, Yee (Protected Horticulture Experiment Station, NHRI, RDA)
  • 발행 : 2008.06.30

초록

수직형에 비해 비교적 가격이 저렴하고 냉난방을 동시에 할 수 있는 농업시설에 적합한 10RT 규모의 수평형 지열히트펌프 시스템을 $240m^2$ 면적의 온실에 설치하고, 이 시스템의 냉방성능을 분석하였다. 응축기 출구온도가 $40^{\circ}C$에서 $58^{\circ}C$로 상승함에 따라 소비전력은 11.5kW에서 15kw로 상승하였으며, 고압이 1,617kpa에서 2,450kPa로 변화하였다. 냉방성능계수는 지중온도 $25.5^{\circ}C$에서 2.7 수준이었으며 지온이 상승함에 따라 하강하여 $33.5^{\circ}C$에서 2.0 수준이었다. 또한 온실 내부로부터 흡수하는 열량(냉방열량)은 같은 지중온도 수준에서 각각 28.8kW, 26.5kW이었다. 가동 8시간 후 지열교환기가 설치된 60cm깊이의 지온은 $14.3^{\circ}C$가 상승하였으며 150cm는 $15.3^{\circ}C$가 상승하였다. 반면 지열교환기가 매설되지 않은 60cm 깊이는 2.4, 150cm 깊이는 $4.3^{\circ}C$의 지온상승을 보였다. 열매 체유가 지열교환기를 통과한 후 평균 $7.5^{\circ}C$의 온포가 하강하였으며, 토양온도가 평균 $27.5^{\circ}C$ 수준에서 토양으로 방출하는 열량은 평균 46kw로 지중열교환기의 단위 길이 당 약 36.8W의 열량을 방출하는 것으로 분석되었다. 팬코일 유닛이 온실로부터 흡수하는 냉방 열량은 평균 28.2kW이었으며, 열매체유의 온도는 $4.2^{\circ}C$ 상승하였다. 축열조내 열전달매체유의 온도가 $26.0^{\circ}C$에서 $2.0^{\circ}C$까지 하강하는데 3시간이 소요되었으며, 평균 축열율은 29.7kW, 총 축열량은 321MJ이었다. 또한 $2.0^{\circ}C$까지 냉열을 축열한 후 $25.4^{\circ}C$까지 방열되는 시간은 외기온이 평균 $28.5^{\circ}C$일 때 4시간이었고, 총 313.0MJ의 에너지가 방열되었으며, 이때 평균 방열율은 21.7kW인 것으로 분석되었다.

It has become a big matter of concerns that the skill and measures against reduction of energy and cost for heating a protected horticultural greenhouse were prepared. But in these days necessity of cooling a protected horticultural greenhouse is on the rise from partial high value added farm products. In this study, therefore, a horizontal type geothermal heat pump system with 10 RT scale to heat and cool a protected horticultural greenhouse and be considered to be cheaper than a vertical type geothermal heat pump system was installed in greenhouse with area of $240\;m^2$. And cooling performances of this system were analysed. As condenser outlet temperature of heat transfer medium fluid rose from $40^{\circ}C$ to $58^{\circ}C$, power consumption of the heat pump was an upturn from 11.5 kW to 15 kW and high pressure rose from 1,617 kPa to 2,450 kPa. Cooling COP had the trend that the higher the ground temperature at 1.75 m went, the lower the COP went. The COP was 2.7 at ground temperature at 1.75 m depth of $25.5^{\circ}C$ and 2.0 at the temperature of $33.5^{\circ}C$ and the heat extraction rate from the greenhouse were 28.8 kW, 26.5 kW respectively at the same ground temperature range. 8 hours after the heat pump was operated, the temperature of ground at 60 cm and 150 cm depth buried a geothermal heat exchanger rose $14.3^{\circ}C$, $15.3^{\circ}C$ respectively, but the temperature of ground at the same depth not buried rose $2.4^{\circ}C$, $4.3^{\circ}C$ respectively. The temperature of heat transfer medium fluid fell $7.5^{\circ}C$ after the fluid passed through geothermal heat exchanger and the fluid rejected average 46 kW to the 1.5 m depth ground. It analyzed the geothermal heat exchanger rejected average 36.8 W/m of the geothermal heat exchanger. Fan coil units in the greenhouse extracted average 28.2 kW from the greenhouse air and the temperature of heat transfer medium fluid rose $4.2^{\circ}C$after the fluid passing through fan coil units. It was analyzed the accumulation energy of thermal storage thank was 321 MJ in 3 hours and the rejection energy of the tank was 313 MJ in 4 hours.

키워드

참고문헌

  1. Cane, D., A. Morrison and K. Christopher. 1998. Operating experiences with commercial ground-source heat pump systems. ASHRAE
  2. Kavanaugh, S.P. and K. Rafferty. 1997. Ground-source heat pumps:Design of geothermal systems for commercial and institutional buildings, ASHRAE
  3. Lee J.H., Y.B. Lee, J.K. Kwon, N.J. Kang, H.J. Kim, Y.H. Choi, J.M. Park, and H.C. Rhee. 2006. Effect of Greenhouse Cooling and Transplant Quality Using Geothermal Heat Pump System. Journal of Bio-Environment control 15(3):211-216 (In Korean)
  4. Lee J.W. 1994. Effect of root zone warming by hot water in winter season on rhizosphere environment, growth and yield of greenhouse-grown cucumber (cucumis sativus L.). PhD diss., Kyungpook Nat'l Univ.:51-55 (In Korean)
  5. Moon J.H., S.K. Lee, and D.K. Ko. 1999. Effect of root zone cooling in summer season on yield and quality. Report of national horticultural research institute: 45-48 (In Korean)
  6. Nam Y.I. 2000. Automatic system of hydroponic culture and production facility. Teaching material of R.D.A. 2000:10-15 (In Korean)
  7. Ryu Y.S., J.T. Chang, Y.J. Kim, K.J. Lee, and J.H. Yun. 1999. Performance test of heat pump system for low temperature treatment of phalaenopsis. Conference of the Korean society of Bio-Environment Control 99:95-99 (In Korean)
  8. Yu I.H., Y.I. Nam, T.Y. Kim, M.Y. Roh, and M.W. Cho. 2006. Effect of Newly Developed Fan and Mist Evaporative Cooling System on Greenhouse Cooling and Growth of Cucumber. Journal of Bio-Environment control 15(1):91-97 (In Korean)