The effect of velocity on heat transfer for water in a tube is shown in Figure 23-3. The higher the value of U, the more easily heat is transferred from one fluid to the other. Alternatively a Swimming Pool Heat Exchanger uses hot water from a boiler or solar heated water circuit to heat the pool water. If T1 and T2 is monitored regularly, one can see the perfomance of the cooling at the delta T. Monitoring this temperature over a longer time, will give indication about the grade of fouling in the heat exchanger. These problems can adversely affect heat transfer and can lead to equipment failure (see Figure 23-1). The cooling water entering the heat exchanger will get warmer on its way through the exchanger. In an open recirculating system, cooling is achieved through evaporation of a fraction of the water. s > 600˚C) ranges, which are of interestin large-scale spray cooling, the effect of water temperature is quite significant as it affects the film boiling close to the surface. The resistance of the tube to heat transfer depends on the material of construction only and does not change with time. Variations in measured values of the U coefficient can be used to estimate the amount of fouling taking place. They can be used with closer approach temperatures, but often become expensive compared to a combination of a cooling tower and a water-cooled exchanger. Conductive heat transfer is proportional to the temperature difference between materials. Most often, the cooling medium is water. An example of a standard liquid cooling loop using a heat exchanger to transfer heat from the liquid to the ambient. 15 CONTROL 15.1 Operating Variables Heat exchangers cooled with water are usually designed for maximum plant throughputs with the cooling water inlet temperature at its peak summer value (typically 21-23°C) and the heat exchanger in its anticipated most fouled state. A common application of these heat exchangers is air-heating coils or air-cooling coils, in which air flows through a finned tube bank to receive heat (heating coil) or dissipate heat (cooling coil). In a shell and tube heat exchanger, one fluid flows through a series of metal tubes and the second fluid is pumped through a shell that surrounds them. A well-designed heat exchanger will take the standard fouling factor for the material it is to handle into account at the specification stage, ensuring that sufficient heat exchange occurs when normal levels of fouling are experienced in operation. The fins increase the surface area and maximize heat transfer to the ambient. Evaporation results in a loss of pure water from the system and a concentration of the remaining dissolved solids. Plate and frame heat exchangers have two rectangular end members holding together a series of metal plates with holes in each corner to allow the liquids to pass through. INTRODUCTION The control of deposits in cooling water systems is It occurs at high temperatures, or when there is low fluid velocity (laminar flow) and uneven distribution of the liquid along the passages and the heat transfer surface. One important operating cost that must be considered is the chemical treatment required to prevent process or waterside corrosion, deposits and scale, and microbiological fouling. KEY WORDS: Heat exchanger, Cooling water, Deposit, Scale inhibitors, Scale, Water chemistry. Outline of Cooling Tower Process A very important concept for understanding cooling tower heat transfer is that of “wet bulb” temperature. Even if this point is not reached, the transfer process is less efficient and potentially wasteful. The size of the exchanger(s) is calculated according to important parameters such as process and water flow velocity, type of shell, layout of tubes, baffles, metallurgy, and fouling tendency of the fluids. The rate of heat transfer, Q, is determined from the equation: Learn more about SUEZ's measurement and control monitoring technology, Chapter 24 - Corrosion Control-Cooling Systems, Chapter 25 - Deposit And Scale Control-Cooling System, Chapter 26 - Microbiological Control-Cooling System, Chapter 27 - Chlorine And Chlorine Alternatives, Chapter 29 - Cooling Tower Wood Maintenance, Chapter 31 - Open Recirculating Cooling Systems, Chapter 32 - Closed Recirculating Cooling Systems, Chapter 33 - Pretreatment Of Cooling Water Systems, Chapter 34 - Air Conditioning And Refrigeration Systems, Control Water Analyses and their Interpretation. Recirculating system, heat exchangers ( as shown in Figure 23-2 and mathematically expressed below treatment programs monitoring the of! A tube is shown in Figure 23-3 conditions that foster them, are affected by temperature foster... Exchanger uses hot water from a boiler or solar heated water circuit to heat flow the. 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