Refrigeration depends upon refrigerant substances that efficiently carry out the

Question

Refrigeration depends upon refrigerant substances that efficiently carry out the refrigeration cycle. The process is based on the well known cooling effect produced by the evaporation of a liquid. NH3 and SO2 were among the first substances used as refrigerants for commercial purposes. The phase diagrams for these two substances are represented in the image below 1. Estimate the range of temperatures at which both 20.0 substances simultaneously exist as liquids at 1 atm of pressure. 10.0 2.0 -NH 0.5 2. Estimate the pressure that needs to be applied to liquefy NH3 at room temperature (300 K) SO 0.1 0.05 0.02 0.01 0.005 A refrigeration cycle using NHa as refrigerant substance is represented in the image below: 150 200 250 300 350 Temperature (K) Describe in your own words the a) phase changes and b) energy transfers that take place in each step of the refrigeration cycle 3. 20.0 10.0 2.0 4. Build an energy transfer versus temperature (E vs. T) plot Cycle that represents the transfer of energy as NHa is taken from point 2 to point 3 in the refrigeration cycle. Clearly justify your reasoning 0.1 0.05 0.02 0.01 0.005 -NH 150 200 250 300 350 Temperature (K)

Explanation / Answer

1): the area between curved line and the vertical red and blue line corresponds to liquid phase.

The temperature and pressure conditions of this region are suitable for the substance to be in liquid phase.

At 1 ATM pressure,the temperature required to be in liquid phase is from 200 K for NH3 and SO2 and up to 225 k for SO2 but it is quite less for NH3. therefore for both of them to exist in liquid phase simultaneously,temp range is from 200k to slightly greater than 200k.

2); the pressure needed to liquify NH3 at room temperature is the y coordinate of the curved line corresponding to 300k, which is around more than 5 ATM.

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