The Influence of Soil Heat Imbalance on Ground-Coupled Heat Pump System and Strategy

Author(s):  
Rui Fan ◽  
Yan Gao ◽  
Yingqian Song ◽  
Weiding Long

It is well noticed that imbalance between winter heat requirement and summer heat gain in soil has an effect on heat transfer characteristic of ground heat exchanger (GHE), which results into the decrease of operation efficiency of ground-coupled heat pump system year by year. Therefore, the research on heat transfer characteristic of GHE for different heat imbalance rate is firstly presented in the article, and then, based on numerical model of heating conduction and groundwater heat advection, the influence of groundwater flow rate is analyzed. Finally, several suggestions such as auxiliary cool and heat source, GHE adjustment strategy are put forward for better and efficient operation of system.

2014 ◽  
Vol 1008-1009 ◽  
pp. 1084-1087
Author(s):  
Ying Bai Xie ◽  
Yi Chen ◽  
Ti Jun Wang

In gas cooler, a key component of transcritical heat pump system, CO2 is always in supercritical status. A well design gas cooler should get the full informations of supercritcal CO2 in-tube cooling heat transfer characteristic. An EES program is developed to calculate the supercritical CO2 cooling heat transfer performances based on 4 selected correlation equations. According to the results and the thermopgysical parameters of supercritical CO2, such as specific heat, density, thermal conductivity and dynamic viscosity, two region, the starting area of supercritical region and the main supercritical region, is suggested for supercritical CO2 cooling heat transfer by temperature at 80°C. In the staring area, the variations of heat transfer and other parameters are intensive, while in the main supercritical region, the variations are clined to be stable.


2009 ◽  
Vol 34 (3) ◽  
pp. 578-582 ◽  
Author(s):  
Yujin Hwang ◽  
Jae-Keun Lee ◽  
Young-Man Jeong ◽  
Kyung-Min Koo ◽  
Dong-Hyuk Lee ◽  
...  

Author(s):  
Chaobin Dang ◽  
Eiji Hihara

Understanding the heat transfer characteristics of supercritical fluids is of fundamental importance in many industrial processes such as transcritical heat pump system, supercritical water-cooled reactor, supercritical separation, and supercritical extraction processes. This chapter addresses recent experimental, theoretical, and numerical studies on cooling heat transfer of supercritical CO2. A systematic study on heat transfer coefficient and pressure drop of supercritical CO2 was carried out at wide ranges of tube diameter, mass flux, heat flux, temperature, and pressure. Based on the understanding of temperature and velocity distributions at cross-sectional direction provided by the numerical simulation, a new prediction model was proposed, which agreed well with the experimental results. In addition, the effect of lubricating oil was also discussed with the focus on the change in flow pattern and heat transfer performance of oil and supercritical CO2.


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