physical and chemical effects on surface

JT Sorption Type Cryocooler

Operation of a sorption compressor is based on the principle that large amounts of gas can be adsorbed on certain solids such as highly porous carbon.The amount of gas adsorbed is a function of temperature and pressure.


Absorption is a Chemical phenomenon or a process in which atoms, molecules, or ions enter some bulk phase.

Adsorption is the adhesion of molecules of gas, liquid, or dissolved solids to a surface. This is physical effect.

Physical and Chemical effects on surface

Adsorption


Typical gas - sorber combinations for sorption cryocoolers


Working of Sorption Type Cryocooler

•By nature, a sorption compressor element is an intermittent system in which the sorbent bed alternates between gas generation and adsorption.

•By combining at least two sorbent beds in a single compressor and sequencing these sorbent beds out of phase, it is possible to produce a constant flow of gas through the cold stage and thus achieve continuous refrigeration.



• The compressor unit contains four sorption cells and two check valves fitted to each cell for controlling control the gas flows.

• Sorption compressor type J-T cryocooler essentially consists of

a) Sorption type compressorb) After coolerc) Return gas heat exchangerd) J-T expansion device



•Usually, heating occurs with an electrical heater and cooling is done by circulating water in a coil around the sorption cell


Valve position in JT cryocooler


• The working fluid is initially heated in the Cell A for ¼ cycle.

• Inlet Valve of A and Outlet Valve of C are opened.

• The hot working fluid is cooled to room temperature in the after cooler.

• The high pressure working fluid at room temperature enters the recuperative heat exchanger, where, it is cooled by the return gas.

• The working fluid is then expanded Isenthalpically by passing through a J-T Valve. Resulting in reduction of temperature.

• The low temperature working substance evaporates as it takes the heating load and produces refrigeration.

• The working substance then enters the return gas heat exchange before getting adsorbed into the Cell C


A B C D


• The type of compression employed in sorption compressor cell is

– Reciprocating type

– Rotary Compressor

– Adsorption type

– None of the above



• Pressure is developed due to

– Adsorption

– Absorption

– Desorption

– Sorption



• Heat exchanger prior to JT valve is used to

– Reduce the temperature before expansion

– To increase the cop

– To remove gaseous heat

– For refrigeration effect



• Adsorption is a ____?

– Physical effect

– Chemical effect

– mostly physical , but in certain cases it is chemical

– Neither physical nor chemical process



• Desorption in a cell comprises of ____?

– Compression

– Expansion

– Combined compression and expansion

– Refrigeration



Cryogenic Engineering By R Barrons

http://www.cryomech.com/

http://www.che.cemr.wvu.edu/publications/projects/large_proj/air.PDF

physical and chemical effects on surface

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