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A Modified Analytical Method for Simulating Cyclic Operation of Vertical U-Tube Ground-Coupled Heat Pumps
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A modified analytical model is presented which discretizes the ground-coupled heat exchanger of a ground-coupled heat pump and utilized a separate cylindrical source solution for each element. First law expressions are utilized for each element to derive a set of fully implicit finite difference equations for the pipe wall temperature and the fluid temperature profile inside the ground-coupled heat exchanger. This method entails less computational overhead than methods which utilize numerical solutions inside the soil, and comes closer than previous analytical methods to satisfying the constant heat flux assumption of the original analytical solution. The thermal capacitance effects of the fluid inside the ground-coupled heat exchanger are included to allow proper prediction of the entering water temperature (EWT) profile at start-up. Comparisons with experimental data on EWT, capacity, energy input and cycling are provided.
Dobson, M. K.; O'Neal, D. L.; Aldred, W. (1994). A Modified Analytical Method for Simulating Cyclic Operation of Vertical U-Tube Ground-Coupled Heat Pumps. Energy Systems Laboratory (http://esl.tamu.edu), Texas A&M University; Department of Mechanical Engineering, Texas A&M University. Available electronically from