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DUCT DESIGN FOR REFRIGERATION AND AIR CONDITIONING
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- 3. The mainpurpose of a duct is to supply conditioned air from the central cooling coil to required buildings And to return the warm air from these buildings to the cooling coil. Duct may comprise a single line or with several branch lines Duct between the blower and the branch lines is often called Main duct. Duct are usually rectangular/square/ circular Fabricated from G.I., black steel, Aluminum, S.S. and Copper. Duct system should transport a given volume of air with minimum pressure drop and heat loss having less noise and vibration.
- 4. PRESSURE DROPS INDUCTS As flow continues in a duct, the static pressure of air drops. This is due to 1. Duct friction 2. Change of direction /velocity.
- 9. METHODS OF DUCTDESIGN Three common methods: i) The equal friction or pressure drop method. Pressure drop/unit length Δp/ΔL is to be taken to be the same for whole system. It is quite suitable when the ducts are symmetrical since pressures are balanced, eliminating the use of dampers
- 10. ii) staticregain method : The drop in pressure during a given length is made up by reducing velocity at the end of the section.
- 11. iii) thevelocity reduction method This a very simple method of duct design. In this case as the flow proceeds, the velocity decreases. The velocity in each duct including main duct is adjusted in order to avoid noise.
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