Design of Ducts: An Industrial Perspective

J. Siddhartha Yadav; B. Gangadhar

Abstract

Central Air Conditioners working is a complex and cumbersome topic which takes a lot of time and effort. It’s a difficult task to explain the entire parts, its working and maintenance. Here an effort is made to explain about the designing of Ducts used in a central A/C. A Commercial building is taken for reference and each floor’s Duct designing is explained. The ground floor is designed with supply air ducts with diffusers without any return air ducts. The first floor is designed with packaged units with return ducts. The second floor is divided into four zones and each zone is supplied with a different type of Air conditioner viz. Zone 1 is supplied with variable refrigerant flow (VRF) with cassette units supplying the air to the room. Zone 2 is supplied with VRF with duct able units without the return air ducts. Zone 3 is supplied with Fan Coil Units (FCU) with chilled water connection. Zone 4 is connected with dedicated VRF system with a designed temperature of 25°C and 25% RH. At the basement the exhaust units are placed. Initially the building survey is done and the commercial building details are studied in detail and the entire floor is divided into zones. Zone 1, Zone 2, Zone 3, Zone 4. For each of the zone the cooling load is calculated and the load found in BTU/hour is converted into tones of refrigeration. Based on this cooling load the ducts designing is done using the EFM (Equal Friction Method). Using the McQuay Software the dimensions of the ducts are decided. Once the dimensions are ready the layout of the building is designed with this Ducts setup in each floor as stated above. AUTOCAD Software was used for the entire design of the ducts. The entire building with the ducts design is provided for optimum air flow in each of the Zone of each floor as the results.

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