The Analysis Of Some Air-conditioning Projects About Ground Source Heat Pump Technology In Wuhan

Closed-loop ground source heat pump air-conditioning system utilizing heat pumpsdischarges heat to the shallow layer soil in summer，and extracts heat from the shallow layer soilin winter to realize refrigeration and heating.Because of its high energy efficiency ratio，it isbeing widely used as an energy saving technology in our country.The application of thistechnology is connected with climate condition，soil condition of the project and other factors.Inthe paper，according to three closed-loop ground source heat pump air-conditioning projects inWuhan，these data on the basis of measurement are calculated and analyzed.Main contents andconclusions are expressed as follows：（1）The measurement and analysis of Exit-Entry Inspection and Quarantine Bureauclosed-loop ground source heat pump air-conditioning project in Hubei province indicates thatsoil temperature shows an increasing tendency in summer and a downtrend in winter.The soiltemperature increased by0.79℃in2010.And it increased by0.23℃when the systemoperated one summer season and two winter seasons.These results indicate that the balance ofsoil temperature is very good.The temperature difference between supply-water and backwateron the used side ranges from1.8to2.2℃in winter and from1.2to2℃in summer.Thetemperature difference between supply-water and backwater on the ground source side is1.05℃in winter and1.1℃in summer.These calculation results show that the temperature ofsupply-water and backwater is in the small range. The system has a cop of2.55in summer and3.6in winter.（2）The measurement and analysis of Qingjiang Garden closed-loop ground source heatpump air-conditioning project shows that the changing tendency and range of soil temperature isnot related to outdoor temperature.The changing range of soil temperature is10.67℃in summerand4.2℃in winter.These results indicate that buried pipe quantity is less than the actualneed.The temperature difference between supply-water and backwater on the used side is2.1℃in winter and2.6℃in summer.The temperature difference between supply-water and backwateron the ground source side is1.7℃in winter and2.6℃in summer.These calculation resultsindicate that the temperature of supply-water and backwater is in the small range. The system hasa cop of3.6in summer and3.15in winter.（3）The measurement and analysis of Wuchang Railway Station closed-loop ground sourceheat pump air-conditioning project shows that soil temperature increased by2.1℃in2008～2009and1.6℃in2009～2010，decreased by1℃in2010～2011and increased by2.7℃in2008～2011.These results indicate that the increased soil temperature may lead to seriousproblem of heat packing.The temperature difference between supply-water and backwater on theused side ranges from3.79to5.43℃in winter and from2.57to3.28℃in summer.The temperature difference between supply-water and backwater on the ground source side rangesfrom2.15to2.39℃in winter and from2.79to3.35℃in summer.These calculation resultsshow that buried pipe quantity is less than the actual need. The system has a cop of1.53to1.74in summer and1.83to2.02in winter. Both outdoor temperature and energy efficiency ofterminal devices have influence on cop.The resistance loss of hygiene hot water circulationpipeline for the project is very big，and this circulation circuit is cut off.It also makes cop small.In order to improve energy efficiency，all factors should be considered to reasonably design thesystem and calculate buried pipe quantity.（4）Taking Exit-Entry Inspection and Quarantine Bureau closed-loop ground source heatpump air-conditioning project as an example，energy consumption simulation calculations byDeST-c software are made. These results show that the first system（cooling water system ofscrew chilled water units and gas-fired boiler）has a cop of1.12in winter and2.06in summer，the second system（direct fired machines using lithium bromide）has a cop of1.22in winter and2.37in summer，and the third system（air-cooling heat pump system）has a cop of0.58in winterand1.31in summer. The cop of above three systems is smaller than the measurement cop of thefourth system（closed-loop ground source heat pump system），which has a cop of2.55in winterand3.6in summer.Obviously，the energy efficiency of this closed-loop ground source heat pumpsystem is higher than other systems.（5）The economy and environmental benefit for the above four systems is calculated andanalyzed.These results show that the initial investment of the fourth system increases by387million yuan than the first system，374million yuan than the second system and391million yuanthan the third system. The annual operation cost of the fourth system decreases by56.07millionyuan than the first system，78.14million yuan than the second system and38.25million yuanthan the third system.Compared with the first system，the static payback period of the fourthsystem is6.9years. Compared with the second system，it is4.79years.Compared with the thirdsystem，it is10.4years. The pollutants discharged by the fourth system are less than othersystems.