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HEATING & CHILLING
SELECTING THE RIGHT INDUSTRIAL CHILLER
Atlas Copco guides you through the process of specifying an industrial chiller, and outlines the factors to consider, including the type of process fluid that will be used, the process cooling temperature, and the chiller size
where production downtime, due to excess heat, is not an option. In recent times there have been major advances and innovations in the design, performance, and efficiency of industrial chiller concepts. The significance of these developments is included in this guide. Among the most compelling reasons for a
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chiller installation is minimising downtime through the continuous protection it provides in removing heat from valuable and temperature-sensitive process equipment. At the same time, a chiller saves water and associated costs by recirculating and re- using the plant’s own water supply. The cost of cooling water can add up
quickly, especially if process equipment is running for several shifts a day. When a chiller is introduced into the system, it can bypass the costs and need for a monitored, municipal water supply and wastewater discharge, and contribute to substantial savings within production budgets. Furthermore, capital investment payback can be realised over a short period of time.
SPECIFYING A CHILLER INSTALLATION
When specifying a chiller installation, a working knowledge of chiller performance factors is crucial to obtaining the right product fit. What needs to be determined is: the type of process fluid that will be used; the process cooling temperature; the flow and pressure requirements; the operating environment; ambient temperature; the chiller size needed and the spatial constraints of its location. The main factors to bear in mind when considering the appropriate cooling fluids for
t is an established fact that industrial chillers are an essential part of manufacturing procedures, especially
Potential users of an industrial chiller system are advised to take into account the conditions in which the process chiller will be used, and the process for which it will be used. This will help to identify the features most needed in the system
a process are their performance characteristics and their equipment compatibility. The performance of a cooling fluid is based
upon its properties at a given temperature. The relevant parameters are specific heat, viscosity, and freezing/boiling points. There is a direct relationship between specific heat and cooling capacity. In order to maintain system integrity and prolong optimum performance, mixing a percentage of ethylene or propylene glycol with water (typically in the 10 to 50% range) is recommended when low or high setpoint temperatures are required. In terms of compatibility, the potential for
corrosion and the early degradation of seals are common failure modes for incorrectly sized systems. That is why the materials of construction and the nature of fluids should be considered, and why inclusion of a corrosion inhibitor in the fluid is recommended. However, in the latest developments of
chiller technology, the storage tank and hydraulic parts of centrifugal pumps are constructed in stainless steel to prevent process water contamination with rust particles, as well as provide higher levels of reliability and temperature control. Similarly, all-aluminium microchannel condensers are designed to provide long life without corrosion and require 30% less refrigerant charge in comparison to other types of heat exchanger. The setpoint temperature will affect the
cooling capacity of a chiller. Decreasing the temperature will put more load on the refrigeration system, and vice versa for increasing it. There is a direct relationship between the temperature at which the chiller has been set and its total cooling capacity. Therefore, it is important to review the chiller’s published performance data for relevance to
20 DECEMBER 2021/JANUARY 2022 | PROCESS & CONTROL
the proposed installation. At the same time, if the chiller is destined for
an exposed site, it is equally important to establish the level of freeze protection required, i.e., the coldest leaving fluid temperature of the chiller during operation.
PRESSURE AND FLOW
While pump life is a primary consideration when configuring an industrial cooling system, pressure loss across the system and the necessary flow rate must first be determined by the pump size and performance. Pressure: An undersized pump will reduce
the fluid flow rate through the entire cooling loop. If the chiller has been equipped with internal pressure relief, the flow will be diverted around the process and back into the chiller. If there is no internal pressure relief, the pump will attempt to provide the
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