Intro to Refrigeration Enthalpy & Gas Laws

Question 1

Charles 1 st Law

Answer 1

p1 x T2 = p2 x T1

Volume is constant

Increase in absolute temperature of an ideal gas whose volume is constant will also result in a proportional increase in pressure of that gas.

Question 2

Charles 2nd Law

Answer 2

V1 x T2 = V2 x T1

Pressure is constant

That increase in the absolute temperature of an ideal gas whose pressure is constant will result in a proportional increase in the volume of that gas

Question 3

Boyles Law

Answer 3

p1 x V1 = p2 x V2

Temperature is constant

That increase in absolute pressure of an ideal gas from which temperature is constant will result in a proportional decrease in the volume of that gas.

Question 4

Bernoulli’s Law

Answer 4

That an increase in the fluid flow results in a decrease in the lateral or static pressure applied by that fluid.

Question 5

Pascal’s Law

Answer 5

Pascals las states that in a closed loop system, a change in fluid pressure results in an equal change in pressure applied through the fluid at a given level

Question 6

Dalton’s Law

Answer 6

That the total pressure of a mixture of gases is the sum of each individual gas pressure.

Question 7

Absolute zero pressure in gauge pressure?

Answer 7

29.92 “hgv

Question 8

Psia ?

Answer 8

PSIG + 14.7

Question 9

What is the ideal gas law formula?

Answer 9

pV=mRT

m= mass
p= Pressure
R= the gas constant
T= Temperature
V= volume

Question 10

General or Combined gas law

Answer 10

p1 x V1 x T2 = p2 x V2 x T1

Pressure
Volume
Temperature

Question 11

Convert formula to Kelvin

Answer 11

K = Deg Celsius + 273

Question 12

Convert to Rankine

Answer 12

Deg R = Deg F + 460

Question 13

kPag to Kapaa

Answer 13

kPa= kPag + 101.3

Question 14

What is heat ?

Answer 14

Energy in a form of molecules in motion.

Question 15

Latent heat

Answer 15

The hidden heat added or removed during a change is state or phase.

Question 16

Specific heat?

Answer 16

The amount of heat in a unitary mass of a substance

Question 17

Sensible heat ?

Answer 17

The visible heat added or removed during a change in temperature.

Question 18

Enthalpy

Answer 18

The amount of heat in one pound of a substance starting from a zero-base point and at universally accepted temperature. The base point of refrigerants is -40 Deg F or C

Question 19

Entropy

Answer 19

A measure of change in a refrigerants molecular activity without a change in molecular structure while passing a vapour through a compressor. Useless heat.

Question 20

Pressure

Answer 20

Force applied over an area

Question 21

Specific Volune

Answer 21

The volume per unit mass of a substance

Question 22

Subcooled

Answer 22

A liquid refrigerant at a lower temperature than it’s saturation temperature for a given saturation pressure

Question 23

Superheat

Answer 23

A refrigerant vapour at a higher temperature than it’s saturation temperature for a given saturation pressure

Question 24

What is Net Refrigeration Effect

Answer 24

Is the amount of heat gained in the evaporator during a refrigeration cycle.
NRE = evaporator outlet enthalpy - metering device inlet enthalpy
NRE = h3-h1

Question 25

Heat of Compression (HOC)

Answer 25

Is the amount of heat added by the compressor and the compression process during the refrigeration cycle.
HoC = Compressor outlet enthalpy - Compressor Inlet Enthalpy
NRE= h5-h4

Question 26

Heat of Rejection. (HOR)

Answer 26

Is the amount of heat rejected by the condensing process during refrigeration cycle.
HOR = Compressor Outlet Enthalpy - Metering device inlet Enthalpy
HOR = h5-h1

Question 27

Mass flow rate

Answer 27

Is the velocity of the refrigerant flowing through the refrigeration system.
m = system capacity / NRE or

200 btu/min / NRE

Question 28

Coefficient of Performance

Answer 28

Is a positive value used to rate the refrigeration system. Higher COP value results in effective system performance.

CoP = NRE / HoC

Question 29

Compression Ratio

Answer 29

Compression ratio is a positive value used to rate a refrigeration system. Lower CR value results in greater system performance

CR = Saturated Discharge Absolute Pressure / Saturated Suction Absolute Pressure

Question 30

Critical point

Answer 30

Is referred to as a refrigerants condition where it’s liquid and vapour form coexist and cannot change state.