Quer y 9Main Hot Water LoopMain Hot Water LoopSongya KeslerSangwooChoSangwooCho06/03/2009(1) Main Hot Water Loop ntsgh ComponeMinimum = 25 HzFrom UtilityThrougPressure = 125 psigTemperature = 180 FSteam supplied from the utility heats the water to the desired setpoint temperature. When heat is need, the 1/3 control valve opens first, then the 2/3 valve. Once the setpoint is reached the valves are slowly closed When hot water is needed the main hot waterreached, the valves are slowly closed. When hot water is needed, the main hot water pump is started. When hot water is no longer needed, the heat exchanger is closed and shortly after, then pumps shut off. (2) Point Summary TableSince the only setpoint is the Supply Temperature, all other data points are either exogenous inputs or system responses, acting to maintain that setpoint temperature. Once again the valves controlhow muchheat is suppliedwhile the pumps controlhow muchagain, the valves control how muchheat is supplied while the pumps control how much water is supplied to the system. The resulting flow rate, differential pressure, and return temperature are results of these controls. (3) Functional Requirements: Supply Temperature – Although the supply temperature appears to be different than the setpoint, this simply shows that the setpoint is not what we previously assumed.{Two days of data are missing in the middle week.MAINHOTWATERLOOP: April 1st, 2009 to April 29th, 2009(3) System Inputs: Steam from Utility –Through Bernoulli’s Equation, peaks in flow rate are matched by dips in pressure.MAINHOTWATERLOOP: April 1st, 2009 to April 29th, 2009(4) System Response: Valve Position –The 1/3 valve is always sufficient to provide enough heat, so the 2/3 is never open. Open the valve more corresponds with faster flow ratesOpen the valve more corresponds with faster flow rates.MAINHOTWATERLOOP: April 1st, 2009 to April 29th, 2009(4) System Response: Pump Speed –A single pump can maintain the necessary pump speed, so pumps are alternated every 7 days to maintain equal wear and teardays to maintain equal wear and tear. Minimum Speed: 25 HzMAINHOTWATERLOOP: April 1st, 2009 to April 29th, 2009(4) System Response: Differential Pressure –The pressure difference is maintained at an estimated setpoint of 19.5 psi.Estimated Setpoint: 19.5 psiMAINHOTWATERLOOP: April 1st, 2009 to April 29th, 2009(5) Outcome Performance: Supply/Return Temperature Difference –The difference in temperature is inversely proportional to the outside air temper atureproportional to the outside air temperature.MAINHOTWATERLOOP: April 1st, 2009 to April 29th, 2009(5) Outcome Performance: Although the supply temper ature does not seem to be related to the steam temperature, there is a correlation with the valve openingcorrelation with the valve opening.MAINHOTWATERLOOP: April 1st, 2009 to April 29th, 2009(5) Outcome Performance: Although the valve position increases both the waterflow rate and supply temperature, the two themselvesdo not appear to be relatedthemselves do not appear to be related. MAINHOTWATERLOOP: April 1st, 2009 to April 29th, 2009(6) System Evaluation• The system as a whole is working well.• Only the Supply Temperature setpoint is below what is expected, but this simply indicates that the actual setpoint is closer to 150 Fthe actual setpoint is closer to 150 F.• Supply/Return water temper ature difference is inversely proportional to the outside airinversely proportional to the outside air temperature.• As the valve opening widens, the supply pg , pp ytemperature and water flow rate increases.• The two pumps effectively alternate every week.GoodBadGoodGood(7) Comparison of Predicted/Measured Data• 143 (Typical Office) –heating only, estimated occupancy levels and manually opened windows, no ceiling fans–Radiant heater 143‐radiators are called“baseboards”in E+;Radiant heater 143 radiators are called baseboards in E+; valve position (unavailable in E+) compared with simulated flow• 145(Representative Office) –same as 143(p )– Radiant heater 145 –same as RH143(7) Comparison of Predicted/Measured DataThe model assumes temperatures rise and decrease during occupied/unoccupied hours respectively. However, the temperature consistently fluctuates without any pattern.(7) Comparison of Predicted/Measured DataIn the model, a huge surge of water passes through the system early in the morning (in preparation for occupied hours); then at night, it comes to a complete stop. When the valve position is more open theposition is more open, the flowrate should increase shortly after. However, the flowratepeaks too quickly; if the valve dl h hflopens steadily, then the flowrateshould increase steadily too.(7) Comparison of Predicted/Measured DataAlthough the setup for rooms 143 and 145 are supposed to be the same, the simulated space ttf 143 i idtemperature for 143 is organized while it is erratic for 145. Nonetheless, the simulated data is much more similar to the actual for room 145.In comparing office 143 with 145, we believe that the difference can be attributed to differentattributed to different schedules used in the simulation.(7) Comparison of Predicted/Measured DataAs stated earlier, if the valve position opens gradually or quickly, then the flowrate should increase equally. This is evident in this comparison. The end points were not accounted for in the simulationthe simulation.(7) Comparison of Predicted/Measured DataWe are unsure as to why the simulated outlet temperature is so different than the actual HWso different than the actual HW return temperature. One thought is that the “outlet node” is in a different theoretical location than the actual return temperature sensor.(7) Comparison of Predicted/Measured Data– Sometimes the model settings that most closely align with predicted data are not the same as the predictedwith predicted data are not the same as the predicted settings. –Model settings are constant during the running g g gperiod, but the schedules are actually different day by day.–Sometimes input simplifications lead to results that more closely follow the actual data than highly sophisticated inputssophisticated inputs.– Examining larger periods of time may produce more meaningful patterns than hourly/daily periods.g p y/ y p(8) Major Model ElementsElements Can BeModeled?Can BeAnalyzed in E+?Interface?WllFllhiht llYESYESWllhihti tWall•Full‐height wall•