The Tri-generation system was tested using the LabVIEW data acquistion system and an array of thermocouples placed at various fluid inlet and outlet ports, as well as in the refrigerator and water reservoir themselves. The fuel consumption over time was measured using a digital scale and timer.The generator was tested under a known load, and the voltage and current drawn measured. The testing bed setup can be seen below:
Flow meters and pressure sensors were not utilized due to budget constraints, so system temperatures at various locations were used to determine the actual system performance.
The first graph shows the fuel consumption over time of the engine as it powers the loaded generator.
A 20 inch high velocity circulating fan and the re-circulating pump used for the water heating unit were loaded to the generator. During the test run the voltage supplied and the current drawn under this load was measured using a multimeter. The voltage and current were 125V and 3.4A. This yields a 425W load on the generator. The fuel consumption rate was then measured over the time of the test run. Measurements were taken roughly every 15 minutes. Comparing the trend of this graph an average fuel consumption rate of 0.0004kg/sec for the given load was calculated.
The second graph below shows the exhaust temperature at the heat exchanger inlet and outlet over time.
The exhaust gas inlet temperature initially jumps to a temperature of 693°C while the exit temperature stays relatively constant at 50°C. The slight drop of the exit temperature correlates to the time periods where the water tank was partially drained and refilled, to prevent boiling within the heat exchanger.
The third graph shows the end temperature of the conduction circuit rod and the temperature within the absorption refrigerator.
The initial and final temperatures of inside the refrigerator were 23.87°C and 3.2°C. The conduction circuit data was plotted on the same graph to compare the rise in conduction temperature to the fall of the refrigerated space temperature. The temperature inside the refrigerator did not significantly decrease until the conduction circuit temperature reached approximately 294°C at a time of roughly 23 minutes. The temperature inside the refrigerator steadily decreased until it reached a steady state temperature of roughly 3°C at time 2 hours and 56 minutes. The temperatures of the conduction circuit and inside the refrigerator then maintained these constant values for the duration of the test run.
The final graph shows the water temperatures at the inlet and outlet of the heat exchanger over time.
From the graph it can be seen that the initial and final temperatures of the water were approximately 23.0°C and 95.0°C respectively. The time it took to reach this maximum final temperature was 1 hour and 43 minutes. This time period is significantly shorter than the time it took the refrigerator to reach its minimum steady state temperature, therefore the water tank was partially drained and refilled multiple times so that operation of the system could continue without damage to the water heating unit. The difference between the inlet and outlet temperatures shows that the water gained an average of 1.6°C after each pass through the heat exchanger based on the flow rate of 7.5gpm through the heat exchanger.
The efficiency of the engine with heat recovery was evaluated and found to be 42.1%. When comparing this efficiency to the assumed efficiency for the engine it can be seen that recovering heat lost through the exhaust gas increased the efficiency of the engine by 17.1%. The total system efficiency at the given load was also calculated and found to be 19.4%. This total system efficiency is a rough estimate considering that the efficiencies of the individual components were unable to be determined and were not included in the calculations.