TF dhCpdT can be applied to a process involving a liquid TF

(T/F) dh-C_pdT can be applied to a process involving a liquid. (T/F) To use Delta u=C_v, Delta T requires that the process be isentropic. (1) Why have European countries banned the use of R-134 in automotive air conditioning systems manufactured after 2011? To achieve the highest possible COP in a vapor-compression refrigeration cycle, we prefer (low/high) temperature differences at the heat exchangers. If we have limited space available for heat exchangers in a vapor-compression refrigeration cycle so that they have to be small in size, the temperature differences at the heat exchangers will need to be (small/large/makes no difference). An air-vapor mixture at 70F with relative humidity of 70% is first heated and then put through a conventional evaporation process that results in a fully saturated mixture at 70F. What is the relative humidity after the heating process? Concerning the banning of chlorofluorocarbons as refrigerants in the early 1990s: Why were they banned? Why do we care about that problem? Define heat.

Solution

1. T

2. F

3. Due to the Excessive emissions that would effect the climate control on porlonged use.

4. High

5. makes no difference

6.

7. a) It effects the Ozone layer

b) if the ozone layer is depleted then our skin will face the many diseases due UV rays coming from sun.

8. The heat is defined as the energy transferred , without transfer of mass, across the boundary of a system because of a temprature difference between the system and surroundings.