Experiment 4 Analysing the thermodynamic cycle of the heat pump using the Mollier diagram PDF

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EXPERIMENT 4: Analysing the thermodynamic cycle of the heat pump using the Mollier diagram

Objectives • To know the basic structure and the application of a Mollier diagram. • To be able to represent the thermo-dynamic cycle of the heat pump in a Mollier diagram using the measured data. • To use the Mollier diagram for determining the mass flow of the coolant.

Apparatus • Heat pump, Joule and Watt Meter , digital Thermometer and, 3 Temperature Sensor,1 digital stopwatch

Experimental set-up

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The equipment was set up as in diagram The copper holders enclosed in the fittings of the heat pump were secured at the temperature measuring points marked with (4) and (5) A drop of oil or heat-conducting paste was brought in each borehole. The temperature sensors were inserted. The temperature measuring points (1) and (2) were prepared with a drop of oil or heat-conducting paste. The red and blue vessels were filled to the 4 l mark with tap water and were positioned around the copper tube windings by their supports.

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The Joule and Watt Meter were connected between mains socket and heat pump and we waited for stabilisation.

Experimental procedure  The Joule and Watt Meter was switched on to turn on the heat pump.  The water in the cold and warm vessel were stirred during a preliminary run of 10 to 15 min.  Values of T1 to T6 were read using thermocouples in as short a time as possible, and also the pressures p1 and p2.  The electrical power consumption P of the compressor was read from the Joule and Watt Meter. Theory • The Mollier diagram encompasses comprehensive statistics about the thermodynamic performance of the used coolant. By means of a few temperature and pressure measurements it gives profound discernment into the thermodynamic cycle of the heat pump. • Mollier diagram pictures the energy and the phase transitions of the coolant in compressor operated heat pumps quantitatively. The x-axis is the specific enthalpy h (kJ/kg) and y-axis is pressure p (bar) of the coolant. For clarity reasons the pressure axis is represented in logarithmic scale. • Enthalpy (joule) is a thermodynamic property of a thermodynamic system. • Enthalpy is used to compute the heat transfer during a quasi-static process taking place in a closed thermodynamic system under constant pressure 23 (isobaric process). Change in enthalpy, ∆H of a system is equal to the sum of non-mechanical work done on it and the heat supplied to it. • The enthalpy h of the gas-liquid depends on the amount x of gas (0...