Tuesday, July 28, 2020

HVAC Chilled Water Distribution Schemes



HVAC CHILLED WATER DISTRIBUTION SCHEMES 
A chilled water system is a cooling system in which chilled water is circulated throughout the building or through cooling coils in an HVAC system in order to provide space cooling. The principal objectives of chilled water pumping system selection and design are to provide the required cooling capacity to each load, to promote the efficient use of refrigeration capacity in the plant, and to minimize pump energy consumption subject to whatever budgetary constraints may apply. 

In the typical design process, such decisions are made on the basis of economic calculations. In chilled water systems, pumping normally draws from around 6 to 12 % of the total annual plant energy consumption. Conventional chilled water plants distribute water at constant flow rate, regardless of the actual cooling demand. Since most air-conditioning systems only reach peak load a few hours a year, energy is wasted by continually running the pumps at constant flow (speed). 

An efficient distribution system use variable flow that tracks the variable thermal load. This course provides a description of common chilled water system types from the most basic constant flow to all variable flow systems along with advantages and limitations. For purposes of discussion, chilled water pumping systems are divided into three categories. 
  1. Constant Volume Chilled Water Systems 
  2. Primary/Secondary Chilled Water Systems 
  3. Variable Primary Flow Chilled Water Systems
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