Simulation of embedded heat exchangers of solar aided ground source heat pump system

Abstract

Aimed at unbalance of soil temperature field of ground source heat pump system, solar aided energy storage system was established. In solar assisted ground-source heat pump (SAGSHP) system with soil storage, solar energy collected in three seasons was stored in the soil by vertical U type soil exchangers. The heat abstracted by the ground-source heat pump and collected by the solar collector was employed to heating. Some of the soil heat exchangers were used to store solar energy in the soil so as to be used in next winter after this heating period; and the others were used to extract cooling energy directly in the soil by circulation pump for air conditioning in summer. After that solar energy began to be stored in the soil and ended before heating period. Three dimensional dynamic numerical simulations were built for soil and soil heat exchanger through finite element method. Simulation was done in different strata month by month. Variation and restoration of soil temperature were studied. Economy and reliability of long term SAGSHP system were revealed. It can be seen that soil temperature is about 3 °C higher than the original one after one year’s running. It is beneficial for the system to operate for long period.

Keywords

solar assisted ground source heat pump (ASGSHP) / soil storage / three dimensional simulations / heating and cooling

References

[1] EsenM.. Thermal performance of a solar-aided latent heat store used for space heating by heat pump[J]. Solar Energy, 2000, 69(1): 15-25

[2] UchinoA., OhtakeH., KawaiH.. Performance evaluation of heat storage in summer season and snow melting in winter season by snow melting system using a ground source heat pump[J]. Memoirs of the Hokkaido Institute of Technology, 2006, 34: 149-154

[3] OzgenerO., HepbasliA.. Modeling and performance evaluation of ground source (geothermal) heat pump systems[J]. Energy and Buildings, 2007, 39(1): 66-75

[4] GaoQ., SpitlerJ. D., LiM., YuM., QiaoG.. Underground thermal energy storage and its effect on ground source heat pump system[J]. Journal of Jilin University: Engineering and Technology Edition, 2006, 36(4): 497-501

[5] ZogouO., StamatolosA.. Optimization of thermal performance of a building with ground source heat pump system[J]. Energy Conversion and Management, 2007, 48(11): 2853-2863

[6] YavuzturkC., SpitlerJ. D., ReesS. J.. A transient two-dimensional finite volume model for the simulation of vertical U-tube ground heat exchangers[J]. ASHRAE Transactions, 1999, 105(2): 465-474

[7] YavuzturkC., SpitlerJ. D.. Field validation of a short time step model for vertical ground-loop heat exchangers[J]. ASHRAE Transactions, 2001, 107(1): 617-625

[8] BernierM. A.. Ground-coupled heat pump system simulation[J]. ASHRAE Transactions, 2001, 107(1): 605-616

[9] LiuF., GuoT., WangY., WengM.-cheng.. Numerical simulation on heat transfer performance of vertical U-tube with different borehole fill materials[J]. Journal of Central South University of Technology, 2006, 13(3): 234-237

[10] LeeC. K., LamH. N.. Computer simulation of borehole ground heat exchangers for geothermal heat pump systems[J]. Renewable Energy, 2008, 33(6): 1286-1296

[11] LuZ., LianZ.-w., LiuW.-w., LanLi.. Numerical simulation and linear heat source integrated model of vertical embedded pipe for ground source heat pump[J]. Journal of Shanghai Jiaotong University, 2008, 42(3): 409-414

[12] YangW.-b., ShiM.-hen.. Numerical simulation on heat transfer process in U-bend ground heat exchanger of ground source heat pump[J]. Journal of Southeast University: Natural Science Edition, 2007, 37(1): 78-83

[13] ZhangT., QiQ., LiuK.-x., LiuL., ZhangL., XuB.-kun.. Temperature measurement based on radialization power for micro-hotplate[J]. Trans Nonferrous Met Soc China, 2006, 16(s2): s780-784

[14] HanZ.-w., ZhengM.-y., KongF.-h., WangFang.. Numerical simulation of solar assisted ground-source heat pump heating system with latent heat energy storage in severely cold area [J]. Applied Thermal Engineering, 2008, 28(11/12): 1427-1436

[15] TuA.-m., DongH., YangW.-b., TongS.-chen.. Simulation research of vertical U-tube ground heat-exchangers based on cylindrical heat source mode[J]. Acta Energiae Solaris Sinica, 2006, 27(3): 259-264