Throughout this lab, the goal was to become familiar with the features and applications of different heat pumps. A heat pump is an apparatus that transfers heat from a colder environment to that of a hotter environment. Such device can be used to heat or cool and area, depending on the mode of the system. The heat pump in the mechanical engineering lab was utilized to observe such properties. During the investigation into the heat pump, the apparatus was analyzed in both modes; heating and cooling. When the heat pump was running, data such as temperature and pressure were measured at various points in the system. Data collection was obtained through electronic and analog readings. These data points allow for the calculation of enthalpy, COP, EER, and other performance features of the pump.
When pressure and temperature values at known points in the system were determined, then enthalpy values could be translated through the supplied Dupont R-22 Refrigerant properties packet. Enthalpy values for location states 1-7 for both heating and cooling modes can be found in the Appendix. Using these enthalpy values, thermodynamic coefficient of performance (COP) can be determined. Equation 1 calculates the thermodynamic COP for heating mode, and Equation 2 does the same thing for cooling mode.
COPtherm=(h2-h5)/(h2-h1) Eq. 1
COPtherm=(h1-h6)/(h2-h1) Eq. 2
In addition to the thermodynamic COP, there is an effective COP value can be determined for both heat pumps modes. Equation 3 underscores the formula needed to determine effective COP for heating mode .
Heating Effective COP: mair(hout-hin) / ?[Qcompressor + Qblower+ Qpumps] Eq. 3
After calculating the heating effective COP, the cooling effective COP can be found using Equation 4.
Cooling Effective COP: mair(hout-hin) / ?[Qcompressor + Qblower+ Qpumps] Eq. 4
Heating and cooling EER values can be determined using Equation 5 below.
EER = COP x 3.412 [BTU/hr]/watt Eq.5
Lastly, it is required that energy transfer of air and water be determined. In order to determine the value for air, Equation 6 must be used.
Qair = Vair x Duct Area x 1/(?) x (h*2 – h*1) = mair(hout-hin) Eq. 6
A very similar approach can be taken to determine the energy transfer of the water. This is illustrated in Equation 7.
Qwater = gpm x 8.345 lb/gal x 60 min/hr x Cp x (Tout – Tin)°F Eq.7
Experimental Setup and Procedure:
Prior to running the heat pump and gathering data, different parts on the experimental setup had to be identified. The heat pump had various tags located at different parts of the apparatus. These tags identified what the part or component was on the heat pump. In an attempt to become more familiar with the heat pump and its components, these tags were linked to corresponding parts on a separate list. Figure 1 highlights this list with numbered tags, and identifies which heat pump component corresponds to the the given tag number.
Figure 1: Heat Pump Components with Appropriate ID #
After the specific components of the heat pump were identified, it was time to run the apparatus and gather data. Professor Freedman turned on the heat pump and made sure it was set to heating mode. The apparatus must warm for 5-10 min before data can be gathered. This ensures that the thermocouples and pressure sensors are reading parameters at the system’s equilibrium running state. After various data points were collected at different parts of the heat pump. The system had to be shut down, and then switched to cooling mode. This part of the lab was also conducted by Professor Freedman. The system was then allowed to reach equilibrium running state, and the same data points were collected.