Study On The Heat Storage And Release Capacity Of Water-bearing Sand Soil With Buried Pipe System

In this paper,the heat source part of the solar-soil source heat pump system in the cold coastal area is studied.The heat source form is buried in the shallow water-bearing sand layer.The experimental study and numerical simulation are used to study the phase change storage and release characteristics of water-bearing soil.The details are as following:Firstly,the experimental study on the water-bearing sand buried heat exchange system is carried out.Sand storage and release experiments is carried out from different moisture content,whether phase change and different system flows.The experimental results show that with the increase of water content of sand,the heat exchange capacity per unit length of the buried pipe in the sand layer increases,and the heat transfer effect is better.The fluid phase change in the sand,which increases the time of heat storage and release,and increases the amount of heat exchange.Compared with the two flow conditions,the storage and release heat effect is best under the flow of 600 L/h condition.Secondly,a numerical model of three-dimensional unsteady water-containing sand buried pipe is established.The water-bearing sand soil is regarded as porous medium,and the fluid phase transition in the sand layer is considered.The experimental and numerical simulation results are compared to verify the correctness of the numerical model under the same conditions.Based on the validated numerical model,the heat transfer performance and the temperature distribution of saturated water sand soil are studied.It is found that under the condition of saturated water sand soil,the the amount of heat exchange with per unit length of buried pipe increases,and the heat storage and release capacity is enhanced.In addition,the heat transfer between the saturated moisture sand soil and buried pipe at different flow rates was simulated,and the optimal flow velocity was obtained.Simultaneously,the saturated moisture sand soil heat exchange considering the buried depth was simulated and selected for practical engineering reference.Finally,the actual project with solar-soil source heat pump using water-bearing sand soil with buried pipe system is designed.The heat transfer numerical model of the water-bearing sand with buried pipe established in this paper,which is used to simulate thesystem operation under the most disadvantageous heating conditions.The results show that after completion of sand soil heat storage,the system can fulfill the room load requirements within 13 h,then the heat supply will be inadequate.The auxiliary heat source needs to be employed to ensure the good heating effect.