Microsoft PowerPoint - Introduction To Heat condenser

Microsoft PowerPoint - Introduction To Heat condenser -...

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Unformatted text preview: Introduction To Heat Introduction To Heat condenser condenser Course By : Prof. Mohajer prepared by: S.M. rafigh 2011 UNIT OBJECTIVES After studying this unit, the reader should be able to • Explain the purpose of condensers in refrigeration systems • Describe water-cooled and air-cooled condensers • List three types of water-cooled condensers • List three types of water-cooled condensers • Describe the operating differences between wastewater and recirculating water systems • Describe the operation and function of a cooling tower • List methods that facilitate low ambient system operation THE CONDENSER • Heat exchange surface that rejects system heat • Rejects sensible heat – Desuperheating vapor refrigerant from the compressor – Subcools refrigerant at the outlet of the condenser • Rejects latent heat during the condensing process • The greatest amount of heat is transferred during the change of state • Condenser is on the high pressure side of the system WATER-COOLED CONDENSERS • More efficient than air-cooled condensers • Water temperature can be maintained • Water temperature directly affects system pressures • Three types of water-cooled condensers – Tube within a tube condenser – Shell and coil condenser – Shell and tube condenser TUBE WITHIN A TUBE CONDENSER • Heat exchange takes place between the fluids in the inner and outer tubes • Refrigerant flows in the outer tube • Water flows in the inner tube efrigerant and water flow in opposite • Refrigerant and water flow in opposite directions to maximize the heat transfer rate • Depending on the construction, the condenser can be cleaned mechanically or chemically Cool water from the cooling tower 85°F Water Water to tower (95°F) Hot discharge gas from the compressor Subcooled liquid to the receiver Cross-Section of a tube within a tube condenser Surrounding air Hot discharge gas from compressor (outer tube) Water from tower (inner tube) Discharge gas transfers heat to both the surrounding air and the water in the inner tube MINERAL DEPOSITS • Heat from the discharge gas causes minerals in the water to come out of solution • These minerals form scale that adhered to the pipes • The scale acts as an insulator and reduces the rate of heat transfer between the refrigerant and the water • Water is chemically treated to reduce the rate of scale formation on the interior pipe surfaces • Dirty condensers lead to high head pressures Cross-Section of a tube within a tube condenser Surrounding air Hot discharge gas from compressor (outer tube) eat transfer between MINERAL DEPOSITS Water from tower (inner tube) Heat transfer between the refrigerant and the water is reduced because of the insulating effect of the mineral deposits WATER TUBES ARE CLEAN 85°F 95°F Discharge gas 200°F 110°F liquid refrigerant to receiver 145°F liquid refrigerant to receiver Scale 85°F 90°F Discharge gas 200°F MECHANICALLY CLEANABLE CONDENSERS • Tube within a tube condenser has end flanges...
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Microsoft PowerPoint - Introduction To Heat condenser -...

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