Condenser (heat transfer)

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The condenser coil of a refrigerator Lednicka Zanussi ZRA 319 SW, celkovy pohled na zadni cast.JPG
The condenser coil of a refrigerator

In systems involving heat transfer, a condenser is a device or unit used to condense a gaseous substance into a liquid state through cooling. In so doing, the latent heat is released by the substance and transferred to the surrounding environment. Condensers are used for efficient heat rejection in many industrial systems. Condensers can be made according to numerous designs, and come in many sizes ranging from rather small (hand-held) to very large (industrial-scale units used in plant processes). For example, a refrigerator uses a condenser to get rid of heat extracted from the interior of the unit to the outside air.

Contents

Condensers are used in air conditioning, industrial chemical processes such as distillation, steam power plants and other heat-exchange systems. Use of cooling water or surrounding air as the coolant is common in many condensers. [1]

History

The earliest laboratory condenser, a "Gegenstromkühler" (counter-flow condenser), was invented in 1771 by the Swedish-German chemist Christian Weigel. [2] By the mid-19th century, German chemist Justus von Liebig would provide his own improvements on the preceding designs of Weigel and Johann Friedrich August Göttling, with the device becoming known as the Liebig condenser. [3]

Principle of operation

A condenser is designed to transfer heat from a working fluid (e.g. water in a steam power plant) to a secondary fluid or the surrounding air. The condenser relies on the efficient heat transfer that occurs during phase changes, in this case during the condensation of a vapor into a liquid. The vapor typically enters the condenser at a temperature above that of the secondary fluid. As the vapor cools, it reaches the saturation temperature, condenses into liquid and releases large quantities of latent heat. As this process occurs along the condenser, the quantity of vapor decreases and the quantity of liquid increases; at the outlet of the condenser, only liquid remains. Some condenser designs contain an additional length to subcool this condensed liquid below the saturation temperature. [4]

Countless variations exist in condenser design, with design variables including the working fluid, the secondary fluid, the geometry and the material. Common secondary fluids include water, air, refrigerants, or phase-change materials.

Condensers have two significant design advantages over other cooling technologies:

Examples of condensers

In laboratory distillation, reflux, and rotary evaporators, several types of condensers are commonly used. The Liebig condenser is simply a straight tube within a cooling water jacket, and is the simplest (and relatively least expensive) form of condenser. The Graham condenser is a spiral tube within a water jacket, and the Allihn condenser has a series of large and small constrictions on the inside tube, each increasing the surface area upon which the vapor constituents may condense. Being more complex shapes to manufacture, these latter types are also more expensive to purchase. These three types of condensers are laboratory glassware items since they are typically made of glass. Commercially available condensers usually are fitted with ground glass joints and come in standard lengths of 100, 200, and 400 mm. Air-cooled condensers are unjacketed, while water-cooled condensers contain a jacket for the water.
Condenser unit for central air conditioning for a typical house Condenser unit for central air conditioning.JPG
Condenser unit for central air conditioning for a typical house

Other Types of Condensers

There are three other condensers used in HVAC systems:

Applications:

   Most common uses for this condenser are domestic refrigerators, upright freezers and in residential packaged air conditioning units. A great feature of the air cooled condenser is they are very easy to clean. Since dirt can cause serious issues with the condensers performance, it is highly recommended that these be kept clear of dirt.

   They also require a cooling tower to conserve water. To prevent corrosion and the forming of algae, water cooled condensers require a constant supply of makeup water along with water treatment.

   Depending on the application you can choose from tube in tube, shell and coil or shell and tube condensers. All are essentially made to produce the same outcome, but each in a different way.

   Typically these are used in large commercial air-conditioning units. Although effective, they are not necessarily the most efficient.

Equation

For an ideal single-pass condenser whose coolant has constant density, constant heat capacity, linear enthalpy over the temperature range, perfect cross-sectional heat transfer, and zero longitudinal heat transfer, and whose tubing has constant perimeter, constant thickness, and constant heat conductivity, and whose condensible fluid is perfectly mixed and at constant temperature, the coolant temperature varies along its tube according to:

where:

See also

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References

  1. Hindelang, Man jjhat; Palazzolo, Joseph; Robertson, Matthew, "Condensers", Encyclopedia of CHemical Engineering Equipment, University of Michigan, archived from the original on 24 December 2012
  2. Weigel, Christian Ehrenfried (1771). Christian Ehrenfried Weigel, Volume 1 (in Latin). Goettingae (Göttingen): Aere Dieterichiano. pp. 8–11. Retrieved 16 September 2019.
  3. Liebig, Justus von; Poggendorff, J.C.; Wöhler, Fr. (eds.) (1842), Handwörterbuch der reinen und angewandten Chemie [Dictionary of pure and applied chemistry], vol. 2 (in German). Braunschweig, Germany: Friedrich Vieweg und Sohn. Article: "Destillation," pp. 526–554.
  4. Kays, W.M.; London, A.L., "Condensers", Compact Heat Exchangers, OSTI, OSTI   6132549