REFRIGERATION
A refrigeration system circulates a fixed inventory of refrigerant to provide a specified amount of cooling at or below a given temperature. The cooling can be provided over a range of temperature as sensible heat from warming of a gas or supercritical stream or at a constant temperature as latent heat from vaporizing liquid. Cooling of the refrigerant stream is done by work expansion of the entire stream or part of the stream. JT expansion and cooling with an external refrigerant may also be employed. A complete refrigeration system includes recycle compression and oil removal; a cold box containing valves, heat exchangers, adsorbers, and expanders; refrigerant storage and distribution; and controls.
The net refrigeration requirement for a system providing liquid as refrigerant is much lower than that of a system of comparable recycle flow that is providing liquid as product. The refrigerator does not provide net cooling from ambient temperature; it just provides the heat of vaporization to cool the load and the additional cooling needed to overcome system losses. Much of the recycle stream is used to deliver the refrigeration but generates little refrigeration itself, only a minor amount of JT cooling. Therefore, a refrigerator will have lower expander power and will often require fewer expanders to optimize cycle efficiency. Use of an external refrigerant is not uncommon, but the flow is typically much less because only enough cooling to overcome warm end losses is required.
Contamination is usually less of a concern in a refrigerator than in a liquefier since there is no feed gas to act as a continual source of impurities. The makeup gas required to maintain system inventory can introduce some contamination into the system, and contamination may also originate from the load, depending upon the application. It is usually sufficient to have just a single adsorber at each appropriate temperature level, and in many cases a single cold adsorber is all that is required.
Cryo Technologies provides helium refrigerators in capacities as low as about 75 W. There is no definitive upper limit on refrigeration power; we will simply design to customer requirements. Refrigeration is provided by turbines, expansion engines, or both, depending upon the application. Units can be designed with or without liquid nitrogen precooling depending upon the availability and cost of liquid nitrogen. Adsorbers can be provided at the 80K and 20K levels and are included as required by the specific application. Computer control is standard, and systems are automated in accordance with customer preferences, including fully automatic startup and shutdown where applicable.
Our helium refrigerator designs incorporate many years of experience in industrial and scientific applications including gas phase, supercritical, and liquid applications across a temperature range from 80K to 3K. A Cryo Technologies helium refrigerator is customized in accordance with the specific requirements of the customer, taking into account the unique operating requirements and economic constraints of each application. Our customers are never limited to the capabilities of an existing design.
In addition to helium refrigerators, Cryo Technologies can provide nitrogen refrigerators where higher refrigeration temperatures are required, such as in high temperature superconductivity applications. Let us know the specifics of your application and we will provide a system to meet your needs.
7.5 KW Helium Refrigerator Cold Box