Design And Application Of Oilfield Produced Liquid Heating Device Based On Phase Change Heat Storage

In order to reduce the cost of direct electric heating of produced liquid in isolated oil Wells,this paper introduces phase-change heat storage technology to reform its heating mode by using peak-valley electricity price difference.Firstly,paraffin wax was used as phase change material,and the initial design of phase change heat storage device was completed according to its key thermophysical parameters and the actual heating requirements of on-site produced liquid.The shell shape,heat exchange tube layout and fin shape of the heat storage device were improved by numerical simulation.The numerical simulation results show that the total melting time of paraffin wax in rectangular heat storage device is the shortest under the same conditions,and the total melting time is shortened by 34.72% compared with that of circular heat storage device.Selecting the improved arrangement of heat exchange tubes can further shorten the time of paraffin wax melting by 23.31%.The total melting time of paraffin wax can be further reduced by 18.39% after adding annular fins outside the heat exchange tube.Secondly,an experimental platform was set up to study the storage and heat release performance of the improved phase change heat storage device.The results show that the increase of heat transfer fluid flow can promote the average power and total heat transfer time in the process of heat storage and release,but it has more obvious effect on the process of heat storage than the process of heat release.When the inlet water temperature is 90 ℃ and the flow rate is 4 L/min,the heat storage time is630 min,and the time required for heat transfer at the same flow rate is 185.17 min.The average storage/heat release power is 2.183 k W and 3.763 k W,respectively.When the flow rate increases from 4 L/min to 7 L/min,the average storage/heat release power increases by 53.83% and 26.89%,and the storage/heat release time decreases by31.75% and 15.03%,respectively.Finally,the economy of the phase change heat storage device is analyzed from the perspectives of net present value,investment return cycle and internal rate of return.The results show that the net present value of the phase change heat storage device in the life cycle is greater than zero when the discount rate is 4%-16%,which has a good investment value.Sensitivity analysis shows that the main factors influencing the investment economy are peak-valley electricity rate difference,heat extraction rate and life cycle.