Heat Interchangers and Heat Exchangers

Heat Interchanges

There are a variety of heat transfer solutions used by the chemical and pharmaceutical industries. Liquids, gases, and solids can all be heated. Condensed steam or heated fluids are used to heat these materials. Operations that involve heat transfer in pharmacy include granulating, crystallizing, evaporating, and distilling starch paste. Industrial processes involve transfer of heat energy in various ways. Through metal walls, heat exchangers are used to transfer heat between one fluid (hot gas or steam) and another fluid (liquid). Using heat exchangers, heat can be transferred from one liquid or gas to another through a metal wall.

The two classifications may be interchangeable at times. When heat is transferred from one side of a tube to another, the film coefficients for both sides of the tube are the same. Combining the increase in one side of the coefficient with the increase in the other side of the liquid velocity should enhance both coefficients. Baffles outside the tubes could be used to increase the flow rate and the heat transfer coefficient. With a baffle arrangement, the second fluid will travel along a longer path and have a smaller cross-section. Consequently, baffles increase the speed of liquid outside tubes and cause it to flow at a right angle to tubes because they are designed that way. As a result, heat transfer outside the tubes becomes more efficient because turbulence is increased.

Baffles

A baffle is a metal disc with one side removed. The perforations in these discs are used to fit tubes through them. The clearance between the baffles, shell, and tubes is kept small to prevent or at least minimize leakage. Metal rods support the baffles and set screws fasten them between the tube sheets. The heat transfer coefficient of the shell side is increased by modifying the flow pattern in parallel or cross flow with the tube bundles. It also has the function of supporting the tube all the way along its length to prevent it from bending. This type of baffle may be segmented horizontally (horizontal baffle) or vertically (vertical baffle) as shown in Figure below.



Baffle windows are cut portions of baffles. It allows fluid to flow through. From 15% to 50% is the baffle window area. At a 20% cut segmental baffle, the portion of the baffle that is cut out corresponds to 20% of the whole baffle. The distance between baffles affects the pressure drop and heat transfer coefficients. A larger spacing decreases pressure drop on the shell side, reduces turbulence, and increases heat transfer coefficient. Smaller spacing increases turbulence and heat transfer, but it may also result in a significant increase in pressure drop, therefore nullifying the advantage from higher heat transfer coefficients. Baffle spacing is chosen in accordance with the allowable pressure drop at the shell side and the desired heat transfer coefficient. Baffles are generally spaced 1/5th of the diameter of the shell.

Heat Exchangers

Many manufactures prefer heat exchangers for cooling control panels and electrical enclosures because they are more efficient than alternative methods. Pharmaceutical production and packaging have also been affected by heat exchanger technology in many of the same ways. Managed electrical waste heat management is key to the pharmaceutical industry, which includes processes such as fine chemistry necessary to create pharmaceutical drugs and products. Manufacturers have benefitted immensely from heat exchangers because they have been able to reliably and consistently cool their technologies without expending excessive energy. The enclosure and cooling of electrical circuits are crucial to prevent overheating. Heat exchangers are much more energy efficient and require much less maintenance than air conditioners. The cost-effectiveness of these machines compares favorably with air compressors.

Thermal management, however, goes far beyond cooling electrical equipment in the pharmaceutical industry. Cosmetics and pharmaceutical solutions often require specific temperatures, mixing times, and temperatures during processing to be combined and mixed. Heat exchangers not only enhance production and ensure a high standard of quality for products, they can also maintain reliable thermal management over the long haul.

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