Heat Rejection Options in HVAC Systems

One of the basic requirements of the air conditioning and refrigeration system is to reject heat to the outdoors. The refrigerant chillers come in two different forms: -An air-cooled chiller uses the flow of outside air across the condenser to remove or reject heat from the chiller. Air-cooled chillers typically have the condenser mounted on the roof or somewhere outside the facility while the evaporator can either be inside or outside the facility. -Water-cooled chillers are typically 100 tons or greater and use water to remove the heat from the condenser. Water-cooled chillers are typically more efficient than air-cooled chillers. The condenser water is kept cool by a cooling tower, or water from the city main or well water is used. A water-cooled chiller will typically have the condenser and evaporator inside a facility while the cooling tower is located outside. In order to properly apply the heat rejection concepts, HVAC designer must be aware of the different heat rejection methods. In this course we will discuss the various heat rejection methods as well the controls that may be used to maintain proper refrigerant and water temperatures. Also presented in the course is the concept of total heat of rejection, its derivation and how it applies to the process of air conditioning. This 4-hour quick book provides a comprehensive description of the five prominent heat rejection methods as applicable to air conditioning systems. This course is applicable to architects, air-conditioning engineers, controls engineers, contractors, environmentalists, energy auditors and loss prevention professionals. It is assumed that all the readers know the basic functioning of the air-conditioning system. Learning Objective This course is intended to provide you with the following specific knowledge and skills: -The concept of total heat of rejection (THR), its derivation and how it applies to the process of air conditioning; -Five prominent methods of heat rejection; -Importance of sub-cooling and super-heat in air-cooled condensers; -Types, rating and selection of air cooled condensers; -Operating principle of wet cooling towers; -Types of cooling towers, cross-flow, counter-flow, induced draft and forced draft; -Capacity control of air cooled and water cooled systems; -Closed circuit fluid coolers v/s evaporative condensers; -Energy performance of air-cooled chiller v/s water cooled systems; -Effectiveness of adiabatic cooling technology; -Benefits and limitations of various heat rejection methods; -The selection of appropriate method on capital costs and environment criteria.