Applications of Refrigeration and Air Conditioning

The fields of refrigeration and air conditioning are interconnected, each has its own province too. The largest application of refrigeration is for air conditioning. In addition, refrigeration embraces industrial refrigeration including the processing and preservation of food, removing heat from substances in chemical, petroleum and petrochemical plants, and numerous special applications such as those in the manufacturing and construction industries.

In a similar manner, air conditioning embraces more than cooling. The comfort air conditioning is the process of treating air to control simultaneously its temperature humidity, cleanliness, and distribution to meet the comfort requirements of the occupants of the conditioned space. Air conditioning, therefore, includes entire heating operation as well as regulation of velocity, thermal radiation, and quality of air, including removal of foreign particles and vapors.

Some applications of refrigeration and air conditioning are as follows :

Air Conditioning of Residential and Official Buildings

Most of the air conditioning units are devoted for comfort air conditioning that is meant to provide comfortable conditions for people. Air conditioning of building is required in all climates. In the summer, living/working spaces have to be cooled and in the winter the same have to be heated. Even in places where temperature remains normal, cooling of the building is required to remove the heat generated internally by people, lights, mechanical and electrical equipment. Further in these buildings, for the comfort, humidity and cleanliness of air has to be maintained. In hospitals and other medical buildings, conditions on cleanliness and humidity are more stringent. There ventilation requirements often specify the use of 100 percent outdoor air, and humidity limits.

Industrial Air Conditioning

The term industrial air conditioning refers to providing at least a partial measure of comfort for workers in hostile environments and controlling air conditions so that they are favorable to processing some objects or materials. Some examples of industrial air conditioning are the following:

Spot Heating

In a cold weather it may be more practical to warm a confined zone where a worker is located. One such approach is through the use of an infrared heater. When its surfaces are heated to a high temperature by means of a burner or by electricity, they radiate heat to the affected area. If a specific area has to be cooled, it will be unwise to cool entire room or factory. In this case, conditions may be kept tolerable for workers by directing a stream of cool air onto occupied areas.

Environmental Laboratories

The role of air conditioning may vary from one laboratory to the other. In one laboratory, a very low temperature, say – 40oC must be maintained to test certain equipment at low temperatures, and in another, a high temperature and humidity may be required to study behavior of animals in tropical climates.

Printing

In printing industries, control of humidity is a must. In some printing processes the paper is run through several different passes, and air conditioning must be maintained to provide proper registration. If the humidity is not properly maintained the problems of static electricity, curling or buckling of paper or the failure of the ink to dry arise.

Textiles

Like paper, textiles are sensitive to changes in humidity and to a lesser extent changes in temperature. In modern textile plants, yarn moves at very high speeds and any changes in flexibility and strength of the yarn because of the change in humidity and temperature will thus affect the production.

Precision Parts and Clean Rooms

In manufacturing of precision metal parts air conditioning helps to (a) keep the temperature uniform so that the metal will not expand and contract, (b) maintain a humidity so that rust is prevented and (c) filter the air to minimize dust.

Photographic Products

Raw photographic materials deteriorate fast in high humidity and temperatures. Other materials used in coating film also require a careful control of temperature. Therefore, photographic- products industry is a large user of refrigeration and air conditioning.

Computer Rooms

In computer rooms, air conditioning controls temperature, humidity and cleanliness of the air. Some electronic components operate in a faulty manner if they become too hot. One means of preventing such localized high temperature is to maintain the air temperature in the computer room in the range of 20 to 23 0C. The electronic components in the computer functions favorably at even lower temperatures, but this temperature is a compromise with the lowest comfortable temperature for occupants. A relative humidity of about 65% is maintained for comfort condition.

Air Conditioning of Vehicles

For comfortable journey, planes, trains, ships, buses are air conditioned. In many of these vehicles the major contributor to the cooling load is the heat from solar radiation and in case of public transportation, heat from people.

Food Storage and Distribution

Many meats, fish, fruits and vegetables are perishable and their storage life can be extended by refrigeration. Fruits, many vegetables and processed meat, such as sausages, are stored at temperatures just slightly above freezing to prolong their life. Other meats, fish, vegetables and fruits are frozen for many months at low temperatures until they are defrosted and cooked by consumer.

UNIT OF REFRIGERATION AND COP

The standard unit of refrigeration is ton refrigeration or simply ton denoted by TR. It is equivalent to the rate of heat transfer needed to produce 1 ton (2000 lbs) of ice at 32 0F from water at 32 0F in one day, i.e., 24 hours. The enthalpy of solidification of water from and at 32 0F in British thermal unit is 144 Btu/lb.