No description available.

A computer simulation of a thermosyphon system allowing load drawoff and non-ideal weather conditions has been developed. The model is restricted to the more common single cover, flat plate collector system. Using an analysis based on the present literature, this model calculates the energy absorbed by the collector, the temperature distribution through the system, and the corresponding flow rate. Experimental data for a non-ideal day is compared to the computer simulation. Results of this comparison indicate that the desired parameters, flow rate, collector inlet and outlet temperatures, and the mean tank temperature can be predicted by this model to within 10 percent.

Although a Transient Simulation Program (TRNSYS) has become a widely used model for simulating a solar energy system, there has not been extensive work done in validating this model with actual data. The approach used to validate this model consisted of a modular buildup of components with validation for each module. Extreme care was taken in choosing the necessary parameters to model each component. Where parameters were not given, they were either derived or reasonable values were selected based upon general conditions prevailing in Central Florida or conditions which are generally true for certain solar hot water systems. The intent of this approach was to avoid forcing the model to fit experimental data. Such forcing can cause present results to correlate favorably, but gives no assurances for model performance in future simulations which may be made for varying conditions or completely different systems. TRNSYS compared favorably with experimental data. The average error for an entire 8 hour simulation with 15 minute intervals was only 3.39 percent for the entire tank and collector combination. The model's major deviations were in the start-up collector outlet temperature and rapid changing in actual hot water demand which the model could not match primarily in amplitude and not phase.

A transient computer model of a forced circulation solar hot water system has been developed. The model allows for capacitance effects by solving the energy balances on a four node model of the solar collector. The tank model is designed to include the presence of an auxiliary heater and to allow for the nonideal condition of load drawoff. Five tests were done to validate the computer model. These tests include a comparison of the computer simulation with experimental data and a model available in the literature. The results of these tests indicate that the computer model is able to predict the collector inlet and outlet temperatures within 10% for typical operating conditions.

Thesis--M. Sc., University of Hong Kong, 1982.

Thesis (M.S.)--University of Wisconsin--Madison, 1981. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 141-143).

No description available.

published_or_final_version / Mechanical Engineering / Master / Master of Science in Engineering

The performance of two innovative collector-loop heat exchangers used in pumped circulation solar water heaters was investigated experimentally and numerically, and TRNSYS simulation models were developed for evaluating long-term performance. The heat exchangers evaluated are a narrow gap mantle on a vertical tank and a falling film system in a standard gas hot water tank. The falling film system is based on minor changes to a mass produced tank and does not require the addition of a special purpose heat exchanger. The heat exchangers were assessed for a range of operating conditions to quantify the overall heat exchanger UAhx value and the effect of thermal stratification in the tank. Flow visualisation experiments and CFD modelling were also performed to provide detailed understanding of the operation characteristics of the heat exchangers. For each heat exchanger, the measured and computed collector loop side heat transfer coefficients were correlated by developing new Nusselt number versus Reynolds and Prandtl number functions. New heat transfer correlations were developed for both types of heat exchanger and have been implemented into full solar water heater simulation models in TRNSYS. Predictions of tank stratification conditions in each heat exchanger were in good agreement with experimental data. Compared to a standard direct circulation system, the annual performance of the mantle system and falling film system are 8% and 18% less respectively. The decrease in system performance is due to the heat exchanger penalty and reduced thermal stratification in the storage tank, however they have the added features of freeze protection and suitability for hard water areas. They are also cheaper to manufacture than convectional heat exchange systems. The annual performance of a falling film solar water heater was shown to be affected by de-stratification if an in-tank electric booster was used. However, improved performance can be achieved if an advanced switching controller is used to modulate the flow rate such that the collector return temperature is always higher than the temperature in the top of the tank.

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1983. / Vita. Abstract. Includes bibliographical references (leaves 80-82). Also available via the Internet.