A SYSTEMATIC APPROACH TO IMPROVING THERMOSYPHON SDHW MODEL PERFORMANCE

摘要

A systematic procedure is used to calibrate a computer model of a thermosyphoning, solar domestic hot -water heating system with a tank-in-tank heat exchanger using data from an indoor solar simulator experimental performance test. Excellent agreement with the experimental collector useful energy gain and the energy delivered during a draw is achieved by ensuring that the model gives an accurate prediction of the temporal history of both the system flow rates and temperatures. The calibrated simulation model is then compared to two additional one-day outdoor tests. Simulation accuracy is greatly improved and confidence in an annual performance prediction is increased. convection driven flows on both sides of the heat exchanger make the performance of the combined system extremely difficult to model. These combinations of heat exchanger and tank have not been studied as extensively as in forced flow situations. Finally, vertical temperature stratification in horizontal tanks is not as well understood as it is in vertical tanks and has a major effect on both collector inlet temperature and thcrmosyphon flow rate (Morrison and Braun, 1985). Tank dcstratification due to conduction between the fluid layers and in the tank wall is simulated in the current model, but dcstratification due to convective mixing in the tank, likely more significant than that due to conduction, is not currently modeled.