technology: 19th-century engine refrigerates without cfcs
The heat pump cycle invented by daniel clery in 1816 is the basis for a new cooling device for home refrigerators, which is completely free of fluorine-chloride (CFC)refrigerants.
Fluorine-containing carbon harms the ozone layer of the Earth.
The cooling unit was developed by Sunpower, Athens, Ohio, using only inert gas helium as a working fluid.
David Berchowitz, design engineer for the project, said the production model may be more effective than a regular refrigerator.
Robert Stirling, a Scottish pastor and inventor, designed the principles of the Stirling cycle.
The cycle can be used as an engine, driven by heat generated outside the engine itself, or as a heat pump, driven by mechanical energy.
For most of the 19 th century, the engine competed with the steam engine until the beginning of the century, when the internal combustion engine replaced the two engines.
However, interest in the Stirling cycle has not disappeared.
Philips, the Dutch electronics company, spent about 1940 pounds on 100 million s and 1950 s trying to develop a small commercial Stirling engine, but eventually gave up the attempt.
NASA is developing Stirling engines for satellites and already has some prototype engines that drive NASA trucks.
Several Japanese companies have sold portable generators and heat pumps based on the Stirling cycle, and an Indian company has developed an aStirling engine to drive generators or pumps running on agricultural waste such as rice shells
Kockums, a Swedish company, is working with German engineering company MAN to develop 12-
A 600 KW-cylinder Stirling engine powered by a submarine.
The potential of the Stirling cycle for refrigeration was first discovered in 1873, but technical problems have not been overcome until recent years.
Remote Sensing satellite of the European Space Agency
1 will be launched next year and it uses the Stirling cycle cooler to keep the IR and microwave radiometers at 70 K.
The basic Stirling engine or heat pump consists of two relative Pistons, the compression piston and the expansion piston, which contain a working fluid and a cylindrical shell in the space between them (see Diagram).
There is also a regeneration substrate between the Pistons-a porous material that acts as a heat exchanger, taking heat from it and returning it to the working fluid.
The refrigeration cycle starts with working fluid in the space between the compressed piston and the matrix, called the compressed space.
This is done at a constant temperature, so it heats up when the fluid shrinks, and some heat is discharged through the casing.
Then, the two pistons move together to push the fluid into the space between the expansion piston and the matrix with a constant volume, that is, the expansion space.
When it passes through the substrate, the working mass deposits heat in the substrate material.
The expansion piston then moves backwards to expand the fluid in the expansion space.
In order to keep the temperature constant when the fluid expands, it is absorbed through the shell.
Finally, the piston moves together to push the working fluid system back into the regeneration matrix with a constant volume.
Asit through the matrix, the fluid absorbs some heat stored there.
Therefore, given the mechanical energy driving the piston, when the fluid expands in the expansion space, the circulation absorbs heat, and when the fluid is compressed in the compression space, it is sprayed again.
The Stirling heat pump has the potential for cleaning, silent operation and high efficiency, but it hinders the development of its working fluid in the casing.
Usually the drive piston needs to be mechanically attached to the housing, but the sealing around the piston and piston is proved to be very difficult.
Sunpower overcomes this problem by sealing the entire seal so there is no chance of a liquid leak.
The piston is driven by a linear actuator inside the housing.
Only the two cables required to drive the actuator need to go through the casing wall.
The friction in the equipment is very small.
All the parts are linear in motion and the pistons rotate around their axis so that they do not really touch the inside of the shell, but are lubricated by working fluid.
Sunpower\'s home refrigerator prototype cooling unit weighs about 8 kilograms. At -
26 degrees system C it can increase the heat by 250 watts at 220 watts of electric input.
It has an added advantage because it can change its heat
There is no ability to improve efficiency.
The normal fridge is turned on and off to change the cooling.
Berchowitz says they are now trying to solve two obvious problems with the cooler: cost and longevity.
The cost can be comparable to the current machine, but \"life is hard to test,\" he said \". However thelow-
The friction properties of the equipment mean that wear should be low.
The company specializes in Stirling cycle technology and is also developing solar generators using Stirling engines (see below)
And some prototypes of cooling devices driven by gas have been made.
The system uses a dual Stirling cycle: a combustion gas to drive the Stirling engine and then a Stirling heat pump to provide cooling.
Both portable
Fluorine-containing carbon harms the ozone layer of the Earth.
The cooling unit was developed by Sunpower, Athens, Ohio, using only inert gas helium as a working fluid.
David Berchowitz, design engineer for the project, said the production model may be more effective than a regular refrigerator.
Robert Stirling, a Scottish pastor and inventor, designed the principles of the Stirling cycle.
The cycle can be used as an engine, driven by heat generated outside the engine itself, or as a heat pump, driven by mechanical energy.
For most of the 19 th century, the engine competed with the steam engine until the beginning of the century, when the internal combustion engine replaced the two engines.
However, interest in the Stirling cycle has not disappeared.
Philips, the Dutch electronics company, spent about 1940 pounds on 100 million s and 1950 s trying to develop a small commercial Stirling engine, but eventually gave up the attempt.
NASA is developing Stirling engines for satellites and already has some prototype engines that drive NASA trucks.
Several Japanese companies have sold portable generators and heat pumps based on the Stirling cycle, and an Indian company has developed an aStirling engine to drive generators or pumps running on agricultural waste such as rice shells
Kockums, a Swedish company, is working with German engineering company MAN to develop 12-
A 600 KW-cylinder Stirling engine powered by a submarine.
The potential of the Stirling cycle for refrigeration was first discovered in 1873, but technical problems have not been overcome until recent years.
Remote Sensing satellite of the European Space Agency
1 will be launched next year and it uses the Stirling cycle cooler to keep the IR and microwave radiometers at 70 K.
The basic Stirling engine or heat pump consists of two relative Pistons, the compression piston and the expansion piston, which contain a working fluid and a cylindrical shell in the space between them (see Diagram).
There is also a regeneration substrate between the Pistons-a porous material that acts as a heat exchanger, taking heat from it and returning it to the working fluid.
The refrigeration cycle starts with working fluid in the space between the compressed piston and the matrix, called the compressed space.
This is done at a constant temperature, so it heats up when the fluid shrinks, and some heat is discharged through the casing.
Then, the two pistons move together to push the fluid into the space between the expansion piston and the matrix with a constant volume, that is, the expansion space.
When it passes through the substrate, the working mass deposits heat in the substrate material.
The expansion piston then moves backwards to expand the fluid in the expansion space.
In order to keep the temperature constant when the fluid expands, it is absorbed through the shell.
Finally, the piston moves together to push the working fluid system back into the regeneration matrix with a constant volume.
Asit through the matrix, the fluid absorbs some heat stored there.
Therefore, given the mechanical energy driving the piston, when the fluid expands in the expansion space, the circulation absorbs heat, and when the fluid is compressed in the compression space, it is sprayed again.
The Stirling heat pump has the potential for cleaning, silent operation and high efficiency, but it hinders the development of its working fluid in the casing.
Usually the drive piston needs to be mechanically attached to the housing, but the sealing around the piston and piston is proved to be very difficult.
Sunpower overcomes this problem by sealing the entire seal so there is no chance of a liquid leak.
The piston is driven by a linear actuator inside the housing.
Only the two cables required to drive the actuator need to go through the casing wall.
The friction in the equipment is very small.
All the parts are linear in motion and the pistons rotate around their axis so that they do not really touch the inside of the shell, but are lubricated by working fluid.
Sunpower\'s home refrigerator prototype cooling unit weighs about 8 kilograms. At -
26 degrees system C it can increase the heat by 250 watts at 220 watts of electric input.
It has an added advantage because it can change its heat
There is no ability to improve efficiency.
The normal fridge is turned on and off to change the cooling.
Berchowitz says they are now trying to solve two obvious problems with the cooler: cost and longevity.
The cost can be comparable to the current machine, but \"life is hard to test,\" he said \". However thelow-
The friction properties of the equipment mean that wear should be low.
The company specializes in Stirling cycle technology and is also developing solar generators using Stirling engines (see below)
And some prototypes of cooling devices driven by gas have been made.
The system uses a dual Stirling cycle: a combustion gas to drive the Stirling engine and then a Stirling heat pump to provide cooling.
Both portable
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