#EXPANSION TANK CHILLED WATER SYSTEM SERIES#

Until recently, flash evaporators were limited to вЂњwater poorвЂќ areas, where there was an abundance of relatively low cost fuel or energy. The number of stages or flashes is determined by the economics of each installation. This reduces the amount of heat required for evaporation. A multistage system extends the flashing and recovery zone by condensing the flashed vapor in each stage by heating the brine prior to the heat input zone. In single stage flash evaporators, there are no regenerative stages to recover the energy of the flashed vapor. Usually, the three sections are combined into one package.

Since the evaporator does no work, the heat reject sections receive essentially all of the energy supplied in the heat input section of the evaporator. The vapor produced in this process is passed through moisture separators and directed either to the heat recovery condensers (for multistage units) or to the third section, the reject condensers. The flashing and recovery sections consist of adequately sized chambers which allow the heated fluid to partially flash, thereby generating a mixture of vapor and liquid. The heat input section, commonly called a brine heater, normally consists of a tubular exchanger which transfers heat from steam, exhaust gas from a turbine, stack gases from a boiler, or almost any form of heat energy. The flashing process can be broken down into three distinct operations: heat input, flashing and recovery, and heat rejection.

Such a system is called a multistage flash evaporator.

#EXPANSION TANK CHILLED WATER SYSTEM SERIES#

A series of these chambers can be maintained at successively lower pressures with vapor flashing at each stage. Upon entering the chamber, a small portion of the heated water will immediately вЂњflashвЂќ into vapor, which is then passed through an entrainment separator to remove any entrained liquid and condense the water vapor. An aqueous solution is heated and introduced into a chamber that is kept at a pressure lower than the corresponding saturation pressure of the heated feed stream. The principle is that of an adiabatic (or iso-enthalpic) expansion of a saturated liquid from a high pressure to a lower pressure, thus generating a mixture of saturated liquid and vapor with the same total enthalpy at the lower pressure.ДЇirst applied for production of distilled water on board ships, flash and multistage flash evaporators have been more recently utilized to evaporate brackish and sea water as well as for process liquids. The simplest continuous evaporation system is the single stage вЂњflashingвЂќ of a heated liquid into an expansion tank or flash pot which is maintained at a lower pressure than the feed. Freese, in Fermentation and Biochemical Engineering Handbook (Third Edition), 2014 5.10 Flash Pots and Flash Evaporators During the initial fill for the system, water is supplied through MU water pumps with a chemical feed system to add chemicals to ensure adequate pH value, which is called the passivation of DM water. A solenoid-operated level control valve is provided to ensure the expansion tank level. Make-up (MU) water is normally provided from the CEP discharge through interlocked operation. There is every possibility of leakage losses in the CCW system in gland packing at pumps, in flanged connections, at plate heat exchanger seals, etc.

An overhead expansion tank of adequate capacity is provided to ensure positive suction to the CCW pumps as well as to allow the expansion of water in the closed circuit. The CCW takes away the rejected heat from all auxiliary coolers and circulates in a closed circuit through the plate heat exchanger by redundant CCW pumps.

The main components of this system are redundant CCW pumps, plate heat exchangers, and overhead expansion tanks. Swapan Basu, Ajay Kumar Debnath, in Power Plant Instrumentation and Control Handbook (Second Edition), 2019 7.2.2.1 Closed/Clarified Cooling Water System Components

Expansion tank chilled water system