p.25
Superheating and Subcooling Effects
What is the significance of pump work in this scenario?
Pump work is neglected as it is very small.
p.13
Wet Compression and Expansion Issues
Why can't an engine or turbine be used in the Saturated Reversed Carnot Cycle?
Because expansion occurs in the wet domain.
p.13
Coefficient of Performance (COP)
What is the Coefficient of Performance (COP) of the Saturated Reversed Carnot Cycle?
It is the same as that of the Reversed Carnot Cycle.
p.20
Reversed Carnot Cycle Applications
What is Area A2 called on a T-S diagram?
The area of throttling loss.
p.39
Coefficient of Performance (COP)
What is the focus of EWING's Construction?
Determination of suction temperature for optimum Coefficient of Performance (COP).
p.20
Reversed Carnot Cycle Applications
What does Area A3 represent on a T-S diagram?
The area of loss in refrigeration effect.
p.22
Isentropic and Isothermal Processes
What happens to heat transfer if the saturated liquid line is vertical?
Heat transferred to increase the temperature of liquid along the liquid saturation line will be zero.
p.28
Isentropic and Isothermal Processes
What happens to the specific isentropic compression work when the evaporator pressure decreases or the condenser pressure increases?
The specific isentropic compression work increases.
p.29
Actual Vapor Compression System Dynamics
What occurs during the pull down period in a vapor compression system?
The evaporator is at room temperature and the compressor starts to decrease the evaporator temperature.
p.7
Refrigerators and Heat Pumps
What is the primary function of a refrigerator?
To maintain a body at a temperature lower than the temperature of the surroundings.
p.5
Carnot Cycle Principles
What does the Carnot efficiency formula represent?
The efficiency of a Carnot cycle, defined as η = 1 - (T2/T1).
p.27
Performance Metrics of Vapor Compression Cycle
What happens to vapor density as pressure decreases?
Vapor density decreases drastically.
p.28
Isentropic and Isothermal Processes
How does the divergence of the constant entropy line on the p-H diagram affect enthalpy?
The difference between enthalpy increases.
p.14
Vapor Compression Cycle Overview
What happens to the refrigerant in the evaporator of a Vapor Compression Cycle?
It absorbs heat and evaporates.
p.27
Performance Metrics of Vapor Compression Cycle
What factors affect mass flow rate in a vapor compression cycle?
Volumetric efficiency of the compressor, condenser temperature, and evaporator temperature.
p.15
Coefficient of Performance (COP)
What does the property relation imply in the context of adiabatic work?
It relates changes in work, heat, and entropy.
p.31
Coefficient of Performance (COP)
What happens if the specific refrigeration effect is higher?
Less mass flow rate of the refrigerant is required for the same cooling capacity.
p.19
Performance Metrics of Vapor Compression Cycle
What does the net work equal according to the 1st law of thermodynamics on a T-S diagram?
The area enclosed by the cycle.
p.6
Reversed Carnot Cycle Applications
What is a key characteristic of the processes in the Carnot cycle?
All processes are reversible.
p.37
Actual Vapor Compression System Dynamics
Why is the expansion valve placed close to the evaporator?
To prevent any pressure loss.
p.5
Carnot Cycle Principles
What is the relationship between total input heat and net output work in a Carnot cycle?
Net output work is equal to total input heat minus the heat rejected, W_net = Q_in - Q_out.
p.34
Actual Vapor Compression System Dynamics
What is the effect of pressure drop in a vapor compression system?
It is equivalent to a drop in evaporator temperature.
p.3
Carnot Cycle Principles
What type of process occurs during the transition from state 3 to state 4 in the Carnot Cycle?
Reversible isothermal process.
p.38
Actual Vapor Compression System Dynamics
What is the primary function of an actual vapor compression system?
To transfer heat from a low-temperature reservoir to a high-temperature reservoir.
p.8
Refrigerators and Heat Pumps
What is one ton of refrigeration equivalent to?
The heat transfer rate required to produce 1 US ton (900 Kg) of ice at 0°C from water at 0°C in 24 hours.
p.27
Performance Metrics of Vapor Compression Cycle
How does the specific volume of saturated vapor change with evaporator temperature/pressure?
It increases with the decrease in evaporator temperature/pressure.
p.29
Actual Vapor Compression System Dynamics
What happens to the evaporator temperature when the compressor is switched on?
It starts decreasing from room temperature to the designed temperature.
p.15
Actual Vapor Compression System Dynamics
What is the steady flow energy equation used for in a reversible process?
It describes the energy changes per unit mass in a steady flow system.
p.26
Performance Metrics of Vapor Compression Cycle
What is the relationship between the loss in Refrigeration Effect (RE) and the specific heat of the liquid refrigerant?
The loss is proportional to the specific heat of the liquid refrigerant.
p.2
Carnot Cycle Principles
What is the relationship between work and internal energy in the Carnot Cycle?
W = U2 - U1 + Q1 for process 1-2 and W = U3 - U2 for process 2-3.
p.28
Isentropic and Isothermal Processes
What is the relationship between evaporator pressure and specific volume?
Decreasing the evaporator pressure increases specific volume.
p.33
Actual Vapor Compression System Dynamics
What leads to pressure drop in the suction line?
Frictional resistance and bends in the tubes.
p.16
Vapor Compression Cycle Overview
What are the four main processes in a Vapor Compression Cycle (VCC)?
Compression, Condensation, Expansion, and Evaporation.
p.6
Reversed Carnot Cycle Applications
What happens when a reversible process is reversed?
All energy transfers are reversed in direction but remain the same in magnitude.
p.2
Carnot Cycle Principles
What replaces the diathermic wall during the reversible adiabatic process (2-3)?
The diathermic wall is replaced with an adiabatic wall.
p.5
Carnot Cycle Principles
What does the symbol 'Q' represent in the context of the Carnot cycle?
It represents heat transfer in the cycle.
p.8
Refrigerators and Heat Pumps
What is the primary function of a heat pump?
To maintain a body at a temperature higher than the surroundings.
p.25
Superheating and Subcooling Effects
What is assumed about the liquid in this context?
The liquid is assumed to be incompressible.
p.11
Reversed Carnot Cycle Applications
Is the Reversed Carnot Cycle practical?
No, it is not a practical cycle.
p.38
Actual Vapor Compression System Dynamics
What are the main components of an actual vapor compression system?
Compressor, condenser, expansion valve, and evaporator.
p.33
Actual Vapor Compression System Dynamics
What happens to pressure from state 1a' to 1''?
There is a pressure drop due to friction and bends.
p.35
Actual Vapor Compression System Dynamics
What is the vapor temperature at the compressor exit compared to the surrounding temperature?
It is more than the surrounding temperature.
p.25
Superheating and Subcooling Effects
How are constant pressure lines in the subcooled region treated for practical purposes?
They are considered to be coincident with the saturated liquid lines.
p.32
Actual Vapor Compression System Dynamics
What is the relationship between h1 - h4 and mass flow rate for refrigerants?
A low value of h1 - h4 requires a high mass flow rate.
p.21
Performance Metrics of Vapor Compression Cycle
What is the impact of the SSS cycle on refrigeration effect?
In the SSS cycle, the refrigeration effect is reduced, represented as area A3, known as loss of refrigeration effect.
p.16
Coefficient of Performance (COP)
What is the formula for the Coefficient of Performance (COP) in a VCC?
COP = Q_effective / W_input.
p.37
Actual Vapor Compression System Dynamics
What causes pressure reduction in the evaporator?
Frictional effects and bends in the evaporator.
p.25
Superheating and Subcooling Effects
What is the relationship between the degree of superheat and the degree of subcool in this context?
The degree of superheat is always greater than the degree of subcool.
p.5
Carnot Cycle Principles
What is the significance of using a pure substance in a Carnot cycle?
It allows for clear definitions of phase changes and thermodynamic properties.
p.17
Performance Metrics of Vapor Compression Cycle
What does the volumetric refrigeration effect represent?
Volumetric Refrigeration Effect = (ṁ * (h1 - h4)) kJ/h.
p.26
Performance Metrics of Vapor Compression Cycle
What is the relationship between Refrigeration Effect (RE) and the latent heat of vaporization?
RE is proportional to the latent heat of vaporization.
p.31
Coefficient of Performance (COP)
For which type of refrigerants is the specific refrigeration effect more significant?
For lighter molecules like NH3 and water.
p.29
Isentropic and Isothermal Processes
What is the adiabatic discharge temperature?
The temperature after compression, determined by the ratio of specific heats.
p.34
Actual Vapor Compression System Dynamics
Why is sufficient vapor velocity important in a vapor compression system?
To ensure that lubricating oil picked up by the vapors can reach back to the compressor.
p.8
Coefficient of Performance (COP)
What is the formula for the Coefficient of Performance (COP) in refrigeration?
COP = Q_desired / W_input.
p.12
Refrigerators and Heat Pumps
What is the comparison based on for the Reversed Brayton cycle and the Reversed Carnot cycle?
The same compression ratio.
p.23
Isentropic and Isothermal Processes
What is the significance of the difference in enthalpy at points 3' and 3'' on the p-h diagram?
The difference is negligible.
p.1
Vapor Compression Cycle Overview
What happens in the condenser of the vapor compression cycle?
The refrigerant releases heat and condenses from gas to liquid.
p.21
Coefficient of Performance (COP)
What is the relationship between COP and the areas in SSS and RC cycles?
The COP can be expressed in terms of areas A1, A2, and other parameters of the SSS and RC cycles.
p.30
Refrigerators and Heat Pumps
What equation is used to find h2 in relation to h1?
h2 - h1 = (T2/Tc) * (s3 - s2).
p.12
Actual Vapor Compression System Dynamics
What is a limitation of the Reversed Brayton cycle?
Limited application in aircraft refrigeration.
p.37
Actual Vapor Compression System Dynamics
Where is the expansion valve placed in an actual vapor compression system?
Very close to the evaporator.
p.20
Reversed Carnot Cycle Applications
What does Area A1 represent on a T-S diagram?
The area of the superheating horn.
p.22
Isentropic and Isothermal Processes
What is the implication of a vertical saturated liquid line on specific heat?
It implies that the liquid specific heat should be small for minimum A2.
p.4
Carnot Cycle Principles
In the Carnot cycle, what does Q1 represent?
The heat absorbed from the hot reservoir.
p.36
Actual Vapor Compression System Dynamics
What is done to reduce pressure loss in the liquid line?
The tube length is shortened.
p.9
Coefficient of Performance (COP)
How does the Coefficient of Performance (COP) of a Reversed Carnot Cycle change with temperature?
COP increases with increasing the lower temperature or decreasing the higher temperature.
p.31
Coefficient of Performance (COP)
Does the specific refrigeration effect depend on the actual mass flow rate?
No, it does not depend on the actual mass flow rate.
p.14
Vapor Compression Cycle Overview
What is the role of the condenser in a Single Stage Saturation Cycle?
To release heat and condense the refrigerant back into liquid.
p.30
Refrigerators and Heat Pumps
What are the condenser and evaporator temperatures for the refrigerant properties discussed?
Condenser temperature is 30°C and evaporator temperature is -15°C.
p.31
Actual Vapor Compression System Dynamics
What does the product of mass flow rate and specific volume at state 1 determine?
The required swept volume flow rate and the physical size of the compressor.
p.24
Superheating and Subcooling Effects
What is the impact of superheating on the area of the superheating horn?
It increases the area of the superheating horn, which can increase compression work.
p.19
Isentropic and Isothermal Processes
What does the area under the curve represent in a T-S diagram?
Work done during the process.
p.6
Reversed Carnot Cycle Applications
What are heat pumps and refrigerators considered in thermodynamics?
They are reversed heat engines.
p.11
Reversed Carnot Cycle Applications
What processes are involved in the Reversed Carnot Cycle?
Isentropic and Isothermal processes.
p.34
Actual Vapor Compression System Dynamics
How much does a pressure drop of 0.1 bar affect the evaporator temperature for R22?
It results in a 1.1 K drop.
p.5
Carnot Cycle Principles
What does 'W_net' signify in the Carnot cycle equations?
It signifies the net work output of the cycle.
p.11
Reversed Carnot Cycle Applications
What is a significant characteristic of the Reversed Carnot Cycle regarding compression and expansion?
There is no issue of wet compression or wet expansion.
p.9
Coefficient of Performance (COP)
Which temperature has a stronger effect on the change in COP of a Reversed Carnot Cycle?
The lower temperature has a stronger effect than the higher temperature.
p.28
Performance Metrics of Vapor Compression Cycle
What is the Mean Effective Pressure for a reciprocating compressor?
Compressor work divided by the swept flow rate.
p.21
Wet Compression and Expansion Issues
What process replaces irreversible expansion in the SSS cycle?
Throttling replaces irreversible expansion.
p.32
Actual Vapor Compression System Dynamics
Why does R 11 require a centrifugal compressor?
Due to low value of h1 - h4 and high value of v1, leading to high swept volume.
p.38
Actual Vapor Compression System Dynamics
What is the purpose of the evaporator in a vapor compression system?
To absorb heat from the environment, causing the refrigerant to evaporate.
p.35
Actual Vapor Compression System Dynamics
What causes the pressure drop in the discharge valve?
The pressure drop in the discharge valve makes it at 2 inches.
p.16
Performance Metrics of Vapor Compression Cycle
What does 'Q_d' represent in the context of the VCC?
Heat transferred during the process.
p.10
Wet Compression and Expansion Issues
What fraction of work output do expansion engines or turbines provide compared to work input?
A small fraction, often lost in overcoming friction.
p.13
Reversed Carnot Cycle Applications
What is a characteristic of the Saturated Reversed Carnot Cycle?
It requires 2 compressors, leading to high initial cost and maintenance.
p.22
Isentropic and Isothermal Processes
What does A2 represent in the context of the saturation lines on the T-s diagram?
A2 will be zero if the saturated liquid line is vertical.
p.4
Carnot Cycle Principles
What does the Carnot cycle represent in a steady flow system?
It represents the net work done and heat transfer in the cycle.
p.2
Carnot Cycle Principles
What type of cycle is the Carnot Cycle?
It is a reversible cycle.
p.22
Isentropic and Isothermal Processes
Under what condition will A1 be zero?
A1 will be zero if the saturated vapor line is vertical or has a positive slope.
p.4
Carnot Cycle Principles
In the Carnot cycle, what does Q2 represent?
The heat rejected to the cold reservoir.
p.36
Actual Vapor Compression System Dynamics
Why is subcooling considered useful in the vapor compression cycle?
It helps in improving the efficiency of the system by reducing the pressure loss.
p.4
Carnot Cycle Principles
What is the significance of the Carnot cycle in thermodynamics?
It sets the maximum efficiency limit for heat engines.
p.17
Performance Metrics of Vapor Compression Cycle
How is the actual refrigeration effect calculated?
Actual Refrigeration Effect = (h1 - h4) - (h3 - h2) kW.
p.27
Performance Metrics of Vapor Compression Cycle
What is the effect of decreasing evaporator temperature on refrigeration capacity?
Refrigeration capacity decreases drastically.
p.25
Superheating and Subcooling Effects
How is enthalpy treated in relation to temperature?
Enthalpy is a function of temperature only.
p.24
Superheating and Subcooling Effects
Why is superheating of the refrigerant leaving the evaporator desirable?
To avoid wet compression.
p.28
Performance Metrics of Vapor Compression Cycle
What is the formula for specific volumic compression work (Wv)?
Wv = (h2 - h1) / (v2 - v1).
p.27
Performance Metrics of Vapor Compression Cycle
What is the relationship between mass flow rate and evaporator temperature?
Mass flow rate decreases with the decrease in evaporator temperature.
p.28
Actual Vapor Compression System Dynamics
What happens to volumic compression work (Wv) as evaporator pressure decreases?
Initially increases, reaches a maximum, then decreases.
p.19
Actual Vapor Compression System Dynamics
What is assumed about the line 2-a-3-0 in the context of compressor work?
It is a constant pressure line.
p.21
Actual Vapor Compression System Dynamics
What do areas A1 and A2 represent in the context of SSS and RC cycles?
Areas A1 and A2 account for the deviation of the SSS cycle from the RC cycle.
p.12
Coefficient of Performance (COP)
What is the refrigerating effect in the Reversed Brayton cycle compared to the Reversed Carnot cycle?
It is less in the Reversed Brayton cycle.
p.2
Carnot Cycle Principles
What happens during the reversible isothermal process (1-2) of the Carnot Cycle?
Heat Q1 enters the system at temperature t1 reversibly.
p.17
Performance Metrics of Vapor Compression Cycle
What is the formula for the refrigeration effect in a vapor compression cycle?
Refrigeration Effect = (h1 - h4) kW.
p.27
Performance Metrics of Vapor Compression Cycle
How does the mass flow rate change with decreasing pressure?
The mass flow rate decreases.
p.3
Carnot Cycle Principles
What happens to heat Q2 during the transition from state 3 to state 4?
Heat Q2 leaves the system at temperature t2 reversibly.
p.29
Actual Vapor Compression System Dynamics
What is a solution to prevent the motor from burning down during the pull off period?
Reduce the mass flow rate to the compressor using a hand valve.
p.34
Actual Vapor Compression System Dynamics
What is the effect of choosing a larger diameter pipe in a vapor compression system?
It leads to lower vapor velocity and reduces pressure loss.
p.15
Performance Metrics of Vapor Compression Cycle
What is the significance of integrating the steady flow energy equation?
It allows for the calculation of work done in a reversible process.
p.24
Superheating and Subcooling Effects
What can cause wet compression in a refrigerant system?
Heat transfer in the tube from the surroundings even after insulation.
p.38
Actual Vapor Compression System Dynamics
What role does the condenser play in the vapor compression cycle?
It removes heat from the refrigerant, causing it to condense into a liquid.
p.21
Wet Compression and Expansion Issues
How does isotropic expansion differ from throttling?
Isotropic expansion provides available work, while throttling does not.
p.24
Coefficient of Performance (COP)
How does superheating affect the Coefficient of Performance (COP) with different refrigerants?
With R12, R134a, and R22, COP may increase, but with NH3, COP decreases due to a large increase in the area of the superheating horn.
p.10
Wet Compression and Expansion Issues
Why is the time taken for one stroke of the compressor insufficient?
It takes less than 0.02 seconds, not enough for all liquid droplets to convert into vapor.
p.10
Wet Compression and Expansion Issues
What happens to liquid droplets at high speeds in the compressor?
They hit the compressor valves like bullets, causing damage.
p.36
Actual Vapor Compression System Dynamics
What is the relationship between liquid temperature at the condenser exit and surrounding temperature?
Liquid temperature at the condenser exit is higher than the surrounding temperature, leading to heat rejection.
p.14
Vapor Compression Cycle Overview
What is the primary function of a Single Stage Saturation (SSS) Cycle?
To compress refrigerant vapor and facilitate heat transfer.
p.2
Carnot Cycle Principles
What is done by the system during the adiabatic process (2-3)?
Work WE is done by the system adiabatically and reversibly at the expense of internal energy.
p.23
Actual Vapor Compression System Dynamics
What do natural occurring substances like H2O, NH3, and CO2 have in common regarding their vapor and liquid lines?
They have symmetrical saturated vapor and liquid lines, resulting in large areas A1 and A2.
p.33
Actual Vapor Compression System Dynamics
What causes further superheating from state 1' to 1a'?
Imperfect insulation of the suction line.
p.38
Actual Vapor Compression System Dynamics
What does the 'Ten Point Cycle' refer to in vapor compression systems?
A detailed representation of the thermodynamic processes in the vapor compression cycle.
p.23
Actual Vapor Compression System Dynamics
How does the area A1 of R22 compare to that of R12?
R22 has a larger area A1 than R12.
p.23
Actual Vapor Compression System Dynamics
What is the characteristic of ethane derivatives like CCl3CF3 regarding their saturated vapor line?
They have positive slopes of the saturated vapor line, so compression usually starts from a superheated state.
p.21
Wet Compression and Expansion Issues
What is the effect of throttling on work output?
During throttling, no work is obtained.
p.19
Wet Compression and Expansion Issues
Why can't net work or heat be simply found by the area enclosed by the cycle during a throttling process?
Because throttling is an irreversible process.
p.18
Performance Metrics of Vapor Compression Cycle
Why does actual compression require more work than isentropic compression?
Due to friction and finite heat transfer to the surroundings, causing entropy to not be constant.
p.31
Coefficient of Performance (COP)
Why is NH3 preferred in refrigeration systems?
Because it has a higher specific refrigeration effect, requiring lower mass flow rate for the same cooling capacity.
p.8
Actual Vapor Compression System Dynamics
What does the equation Q_input = Q_effect + W_input represent?
The relationship between heat transfer and work input in refrigeration systems.
p.19
Coefficient of Performance (COP)
What does the equation W = Q1 - Q2 represent in the context of work?
Net work is equal to the heat input minus heat output.
p.32
Coefficient of Performance (COP)
How does R 22's RE and work compare to NH3?
R 22 has less RE and less work compared to NH3.
p.17
Actual Vapor Compression System Dynamics
What is the relationship between mass flow rate and swept volume in a vapor compression cycle?
The mass flow rate of the refrigerant is related to the swept volume (Vs) and the specific volume at the inlet of the compressor.
p.26
Performance Metrics of Vapor Compression Cycle
How does the Refrigeration Effect (RE) change with a decrease in evaporator temperature at a fixed condenser temperature?
RE decreases due to the positive slope of the saturated vapor line.
p.20
Reversed Carnot Cycle Applications
What is the significance of considering a constant pressure line in the alternate approach?
It helps in analyzing work representation on the T-S diagram.
p.31
Coefficient of Performance (COP)
What is the specific refrigeration effect?
The difference between h1 and h4 in kJ/kg.
p.15
Isentropic and Isothermal Processes
What happens to the entropy change (ds) when dQ = 0?
ds = 0, indicating an adiabatic process.
p.8
Refrigerators and Heat Pumps
What is the desired effect in refrigerators called?
Cooling effect or cooling load, measured in Ton of refrigeration (TR).
p.14
Vapor Compression Cycle Overview
What is the significance of the expansion valve in the Vapor Compression Cycle?
It reduces the pressure of the refrigerant before it enters the evaporator.
p.38
Actual Vapor Compression System Dynamics
How does the compressor function in a vapor compression system?
It increases the pressure of the refrigerant vapor, raising its temperature.
p.29
Isentropic and Isothermal Processes
Why does the compressor require cooling when using ammonia?
Because of the high adiabatic discharge temperature.
p.8
Coefficient of Performance (COP)
How is the COP for a heat pump calculated?
COP = Q_H / W_input, where Q_H is the heat delivered.
p.30
Refrigerators and Heat Pumps
What is the temperature (Tc) and pressure (Pc) at the condenser for NH3?
Tc = 30°C and Pc = 11.66.
p.35
Actual Vapor Compression System Dynamics
What is done to reduce pressure loss in the discharge line?
The tube length is shortened.
p.30
Refrigerators and Heat Pumps
What is the enthalpy (h3) and (h4) for NH3?
h3 = h4 = h3f = 341.8 kJ/kg.
p.24
Superheating and Subcooling Effects
Why is subcooling of the refrigerant leaving the condenser required?
It increases the RE and ensures only liquid refrigerant enters the expansion device.
p.1
Vapor Compression Cycle Overview
What occurs in the evaporator of the vapor compression cycle?
The refrigerant absorbs heat and evaporates from liquid to gas.
p.21
Actual Vapor Compression System Dynamics
What is the main difference in appearance between SSS and RCC?
The appearance of the superheating horn (area A1) in SSS is due to dispensing with the isothermal compressor in the RC cycle.
p.9
Coefficient of Performance (COP)
What is the relationship between input work and desired COP in a Reversed Carnot Cycle?
Desired COP is calculated as the ratio of heat input to work input.
p.11
Reversed Carnot Cycle Applications
How many compressors and expanders does the Reversed Carnot Cycle require?
Two compressors and two expanders.
p.29
Isentropic and Isothermal Processes
Why can't ammonia be used in hermetic sealed compressors?
Due to the need for cooling of the compressor by water.
p.32
Actual Vapor Compression System Dynamics
What does the swept volume (Vs) depend on for a refrigerant?
It depends on mass flow rate (m) and specific volume (v1).
p.32
Coefficient of Performance (COP)
What is the significance of COP in relation to different refrigerants?
COP is almost the same for all refrigerants despite differences in RE and work input.
p.18
Refrigerators and Heat Pumps
Why is isothermal compression not possible for a refrigeration cycle?
1. The inlet temperature to the compressor is lower, preventing heat rejection. 2. The exit temperature is higher than the surroundings, but there is insufficient time for heat rejection.
p.10
Wet Compression and Expansion Issues
Why can't turbines be used with two-phase substances?
Turbines can only be used with either liquid or vapor.
p.3
Carnot Cycle Principles
What occurs during the reversible adiabatic process from state 4 to state 1?
Work W_P is done upon the system adiabatically and reversibly, increasing the internal energy.
p.15
Carnot Cycle Principles
What does the equation W = -∫(v dp) represent?
It represents the work done during a reversible process in a steady flow system.
p.1
Vapor Compression Cycle Overview
What is the primary function of the vapor compression cycle?
To transfer heat from a low-temperature reservoir to a high-temperature reservoir.
p.35
Actual Vapor Compression System Dynamics
Why is heat rejection at the compressor exit beneficial?
It helps reduce the load on the condenser.
p.38
Actual Vapor Compression System Dynamics
What happens in the expansion valve of a vapor compression system?
The refrigerant expands, dropping in pressure and temperature.
p.18
Isentropic and Isothermal Processes
Why is isothermal compression adopted as standard for air compressors?
Because it requires less work by maintaining temperature while pressure increases.
p.18
Isentropic and Isothermal Processes
What is the relationship between work done and heat rejection in isothermal compression?
The work done is equal to heat rejection.
p.3
Carnot Cycle Principles
How many reversible adiabatic and isothermal processes constitute a Carnot Cycle?
Two reversible adiabatic and two reversible isothermal processes.
p.32
Performance Metrics of Vapor Compression Cycle
How does the cooling capacity of R 22 compare to R 12 when using the same compressor?
R 22 provides more cooling capacity than R 12.
p.1
Vapor Compression Cycle Overview
What are the main components of a vapor compression cycle?
Compressor, condenser, expansion valve, and evaporator.
p.1
Vapor Compression Cycle Overview
What is the purpose of the expansion valve in the vapor compression cycle?
To reduce the pressure of the refrigerant before it enters the evaporator.
p.33
Actual Vapor Compression System Dynamics
What occurs at the suction valve of the compressor?
Further drop in pressure, reaching state 1'''
p.14
Vapor Compression Cycle Overview
What is the typical cycle used in refrigeration and air conditioning systems?
The Vapor Compression Cycle.
p.23
Isentropic and Isothermal Processes
Why is the constant temperature line not exactly vertical on the p-h diagram?
Because the enthalpy at points 3' and 3'' is not the same, although it is shown as the same in the figure.
p.15
Actual Vapor Compression System Dynamics
What is neglected when integrating the steady flow energy equation?
Kinetic energy (KE) and potential energy (PE).
p.1
Vapor Compression Cycle Overview
What role does the compressor play in the vapor compression cycle?
It compresses the refrigerant, raising its pressure and temperature.
p.18
Performance Metrics of Vapor Compression Cycle
What is the formula for calculating actual work in relation to isentropic work?
Actual Work = Isentropic Work - Isentropic Efficiency.
p.10
Wet Compression and Expansion Issues
What is a consequence of liquid refrigerant droplets in the compressor?
They dissolve lubricating oil, increasing wear and tear.
p.16
Actual Vapor Compression System Dynamics
What is the significance of the enthalpy values (h1, h2, h3, h4) in the VCC?
They represent the energy states at different points in the cycle.
p.12
Coefficient of Performance (COP)
How does the work required in the Reversed Brayton cycle compare to the Reversed Carnot cycle?
It is more in the Reversed Brayton cycle.
