Is the ideal vapor compression cycle internally reversible?
The ideal compression refrigeration cycle is not an internally reversible cycle, since it involves throttling which is an irreversible process.
What is the difference between ideal vapor compression cycle and actual vapor cycle?
The major difference between ideal and actual vapor compression cycle in throttling is the enthalpy. The fluid entering the throttling valve in actual vapor compression cycle has lower enthalpy than in ideal vapor compression cycle and saturated liquid state.
Why are Vapour absorption system better than compression system?
The major Difference between Vapor Compression and Absorption System is that Vapor Absorption System takes in low-grade energy as waste heat from the furnace, exhaust steam, or solar heat for its operations.
Why is throttling valve not replaced by an isentropic turbine in the ideal Vapour compression refrigeration cycle?
Why is the throttling value not replaced by an isentropic turbine in the ideal vapour compression refrigeration cycle? Because the feed is a liquid and the effluent is fairly low quality, the average specific volume of the working fluid in the turbine is very small. the turbine will produce very little work.
Why turbine is not used in place of expansion valve?
Expansion valve has diaphragm and sensing element or power element where it sensed load and according to that diaphragm functions and controlled flow of liquid refrigerant to freezer. turbines can not handle variable load conditions .
Why isentropic expansion is not used in Vcrs?
Because specific volume of liquid is very much lesser than that of vapours,expansion work will be very low[dw=-v(p2-p1)] reversible. This expansion work which is isentropic will not justift the cause of expansion as expansion work becomes lower than friction work. So throttling process is done in case of vcrs.
Why is dry compression preferred as compared to wet compression in Vcrs?
The difference between the wet and dry compression is the working fluid. This means that during dry compression liquid will be in saturated vapor state or superheated state. Saturated vapor state is the one in which the refrigerant is in vapor state entirely and it does not have any liquid.
Is wet compression preferred over dry compression?
Wet compression is preferred over dry compression. Explanation: Dry compression is always preferred. Explanation: It absorbs heat from the surroundings by evaporation.
How do you prevent wet compression?
Wet compression is undesirable as there may be accumulation of liquid inside the cylinder, which in turn will wash away the lubricant resulting in severe mechanical difficulties. Thus, to avoid this, a 5 to 20 K superheat of the refrigerant is always desirable.
What are the disadvantages of wet compression?
Disadvantages of Using Wet Steam
- Corrosion and Scaling. As steam evaporates from the boiler drum, it leaves back the impurities in the drum.
- Water Hammer. Wet steam can increase the chances of occurrence of water hammer.
- Reduced heat transfer.
- Increased load on steam traps.
- Damage to equipment.
What is the disadvantage of steam?
Disadvantages: Steam engines are usually huge and heavy. Because of this, it is tough to transport them from one place to another. Steam engines have a lower efficiency as compared to other heat engines.
Why is wet compression compressing a 2 phase mixture avoided in refrigeration?
Moran and Shapiro (2000) state that wet compression is generally avoided because the presence of liquid droplets can damage the compressor and that in actual systems the compressor handles vapor only (dry compression).
What is wet compression?
Wet compression is a patented process that increases the capacity of a combustion turbine (CT) by as much as 15 to 25% by purposely injecting water droplets into a compressor inlet (AKA – overspray, high fogging or supersaturation).
What is the reason for wet compression?
A wet compression test is similar to a dry compression test except it has the addition of oil placed in each cylinder. A wet compression test is done for two reasons: One or more cylinders has a reading of less than 100 psi on the dry compression test.
What is used as an intercooler in multistage compression of Vapour compression refrigeration system?
Intercooling of the vapour may be achieved by using either a water-cooled heat exchanger or by the refrigerant in the flash tank. Moreover, with water cooling the refrigerant at the inlet to the high stage compressor may not be saturated. Water cooling is commonly used in air compressors.
Which of the following is the merit of compound or multistage compression?
Advantages of multistage compression are: This makes compressor lighter and cheaper. 4) Heat removal during condensation is reduced hence size of condenser is reduced. 5) Volumetric efficiency of compressor increases due to reduced pressure ratio in each stage. 6) Temperature at end of compression would be less.
Which of the following are the main components of Vapour compression system?
The Vapor Compression Refrigeration Cycle involves four components: compressor, condenser, expansion valve/throttle valve and evaporator. It is a compression process, whose aim is to raise the refrigerant pressure, as it flows from an evaporator.
Does superheat ever occur in the condenser?
Let’s start with superheat: Boiling is when a liquid gains heat and transforms into a vapor. Superheat occurs when that vapor is heated above its boiling point. While evaporation and superheat occur in the evaporator, condensation and subcooling occur in the condenser.
What is a good superheat for 134a?
Superheat for most systems should be approximately 10F measured at the evaporator; 20F to 25F near the compressor. If the suction pressure is 45 psi, (which converts to 22F) and the suction temp is 32F, the system still has 10F of superheat.
What is the degree of superheat?
the degree of superheat can be defined as the amount by which the temperature of a superheat vapour/steam exceed the temperature of the saturated vapour/steam at the same pressure.
What is the degree of superheat and dryness fraction?
1) Dryness fraction is defined as the ratio of the mass of actual dry steam to the mass of steam containing it. 4) Degree of superheat is the numerical amount by which the temperature of a superheated vapour exceeds the saturation temperature at the same pressure.