Ground-Source Heat Pump Design Method Based On Thermal Response Of Long-Term Load

Ground source heat pump technology with significant advantage of environmentally friendly, energy saving, high efficiency, low running costs and so on. But so far, because of its high initial investment, ground source heat pump technology account for only a small part in the use of central air condition. The initial investment of ground source heat pump mostly in outdoor underground pipe, estimated accounted for more than 50% of the system, so design the ground heat exchanger reasonable is the key to reduce the initial investment.To ignore the thermal interference between adjacent holes, take half of the drill spacing at distal radius, where establish the adiabatic boundary condition, and establish second boundary condition of time-varying in the borehole wall, and use separation variable method and Green's function method to calculate this heat transfer model to arrive the analytical solution of variable heat flow infinite column heat source outside the hole. Since the form of analytical solution is too complex, this paper use the method of abroad for reference to simplified the heat transfer model, making the computer calculation much faster.Base on variable heat flow infinite column heat source heat transfer model, a ground source heat pump system method of design based on long-period load thermal response was proposed. The method make depth of the hole and outlet temperature of pipe coupling, to design suitable drilling depth, making in that depth of the drilling condition, the pipe outlet temperature still meet the design requirement after running ten years later.Comparing this design approach and the method of "Technical code for ground-source heat pump system"(hereinafter referred to as "Code")provided, obtained the length of the pipe under different maximum outlet temperature, and analysis the long-period operating characteristics of outlet temperature of pipe and the soil temperature distribution around the pipe.