Refrigeration system, purpose

Capacity Control The simplest way to regulate the capacity of most steam vacuum refrigeration systems is to furnish several primary boosters in parallel and operate only those required to handle the heat load. It is not uncommon to have as many as four main boosters on larger units for capacity variation. A simple automatic on-off type of control may be used for this purpose. By sensing the chilled-water temperature leaving the flash tank, a controller can turn steam on and off to each ejector as required. 

Rail traffic is mainly in purpose-built, insulated wagons, many of these having self-contained refrigeration systems. Some produce is pre-cooled and/or iced. Re-icing stations are available on the longer routes in Europe. 

As it turned out, CFCs were ideal for the purpose. The members of this chemical family are nonflammable, noncorrosive, nontoxic, odorless, and very stable. Within a short period, they became widely popular for a variety of industrial applications. In addition to their applications in refrigeration systems, they became popular as aerosol propellants, cleansing agents for electrical and electronic components, and foaming agents in the manufacture... 

For a real refrigeration system, increasing Tc is hardly an option if refrigeration is required at a particular value of Tc. Decreasing TH is no more realistic, because for all practical purposes, Th is fixed by environmental conditions, and not subject to control. 

The workimg medium in refrigeration systems is called the refrigerant. Fluids used for this purpose should ideally be nontoxic and chemically inert, with low boiling points93,94. They should have high enthalpies of vaporization per unit mass, high vapor densities and low miscibilities with water, since the latter can lead to freezeup in the expansion devices or corrosion. 

Refrigerator Capital Costs In small and intermediate size systems the capital cost of a refrigeration system scales more slowly than the refrigeration power. In the limit of large systems, however, the system cost probably varies approximately as the refrigeration capacity. This is not exactly true since a long, low-loss line will require more circulation pumps and compressor stations than a short lossy line of the same total dissipation. For our purposes we assume the refrigerator capital cost to be proportional to the power input to the... 

Automotive refrigerant systems are not composed of refrigerant alone. For lubrication purposes, an oil such as Mobil Artie EAL 68 is used. The significance of this is... 

The purpose of the expansion valve is to control the flowof refrigerant from the high-pressure condensing side of the system into the low-pressure evaporator. In most cases, the pressure reduction is achieved through a variable flow orifice, either modulating or two-position. Expansion valves maybe classified according to the method of control. 

Since the purpose of a refrigeration or air-conditioning system will be to reduce or maintain temperature, a thermostat will usually be fitted to stop the equipment or reduce its capacity when the required condition is reached. The following types are in use ... 

Purpose-built heat pumps will have no cooling function, but operate only to draw heat from a low-temperature source and reject this to a load at a higher temperature. There is no reversal of the refrigerant flow, so the selection and design of the system can be optimized for the duty... 

The purpose of a control system on a refrigeration or air-conditioning plant is to ... 

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