Chilled-water Generation

Chilled water can be generated using heat pumps. They can be either absorption or mechanical chillers. Absorption chillers, which use waste heat (as a source of thermal energy) rather than mechanical/shaft energy for operation, can be economical. Heat source for an absorption chiller can be LLP steam (at 1.5 barg) or a hot process stream. Lithium bromide (LiBr) absorption pumps are frequently used due to their lower cost and application range down to the freezing point of water. 

A large COP indicates more cooling by using external heat. 

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An integrated process for producing chlorine dioxide that can consume chlorine (46) involves the use of hydrochloric acid as the reductant. The spent chlorine dioxide generator Hquor is used as feed for chlorate production, and hydrogen gas from chlorate production is burned with chlorine to produce hydrochloric acid. The principal disadvantage in the integrated hydrochloric acid-based processes is that the chlorine dioxide gas contains Y2 mole of chlorine for each mole of chlorine dioxide produced. A partial purification is achieved by absorption in chilled water in which the solubiHty of chlorine is less than chlorine dioxide however, this product stiU contains 10—15% chlorine on the basis of total chlorine and chlorine dioxide. 

Nominal tonnage capacities range from 60-1,700 tons of refrigeration producing chilled water at 45°F. One unique feature of this system is the use of low pressure steam for the operation of the generator. 

The production of benzylpenicillin is very sensitive to temperature. A lot of metabolic heat is generated and the fermentation temperature has to be reduced by controlled cooling. This heat transfer is achieved by circulating chilled water through banks of pipes inside the vessel (which also serve as baffles) or through external limpet coils on the jacket of the vessel. These coils consist of continuous lengths of pipe welded in a shallow spiral round the vessel. This cooling water system is also used to cool batched medium sterilized in the vessel prior to its inoculation. 

P IDs should be developed for each individual air handling system. The HVAC discipline should generate P IDs for chilled water and hot water. Each of these systems should be independent from similar process-related systems and should be the responsibility of HVAC engineers, not process engineers. The HVAC department may also be required to produce P IDs for other general utilities. 

HVAC, chilled water, and hot water P and IDs are generated independently of process-related systems and have been checked using a P and ID checklist. 

So it is important to vent off some vapor to get rid of the ethane, but not too much. The vent valve (AC) is split-range, so that it is closed when the pressure controller output signal is 83% of full scale. It is wide open when the controller output is at 0%. The sizing of the steam, chilled water, and vent valves is critical to the safe and efficient operation of this batch reactor. Figure 4.42 gives a sketch of the reactor, the controller, the setpoint generator, and the three control valves. 

When a zone is within the comfort gap, its reheat coil is turned off and its VAV box is closed to the minimum flow required for air refreshment (Figure 2.6). When all the zones are inside the ZEB, HW (hot water), CHW (chilled water), and STM supplies to the airhandler are all closed and the fan is operated at minimum flow. When all other airhandlers are also within the ZEB, the pumping stations, chillers, cooling towers, and HW generators are also turned off. 

The x-ray tube assembly is a simple and maintenance-free device. However, the overall efficiency of an x-ray tube is very low - approximately 1% or less. Most of the energy supplied to the tube is converted into heat, and therefore, the anode must be continuously cooled with chilled water to avoid target meltdown. The input power to the sealed x-ray tube ( 0.5 to 3 kW) is therefore, limited by the tube s ability to dissipate heat, but the resultant energy of the usable x-ray beam is much lower than 1% of the input power because only a small fraction of the generated photons exits through each window. Additional losses occur during the monochromatization and collimation of the beam (see section 2.3). 

If only oxygen and a small amount of nitrogen are required as products, a significant portion of the air is a vailable as a nitrogen-rich waste gas. Chilled water can be generated in a humidification to wer by passing that waste gas countercurrently... 

These types of chillers are corrrmonly used in gas or kerosene operated refrigerators. The difference is that here solar-heated water would be used to provide heat irrput in the generator (see Fig. 19). In the system shown the refrigerant is expelled from the rich solution and the weakened solution is returned to the absorber. The refrigerant vapor dissipates some of its heat to the environmerrt (may be water cooled) and condenses. This Uqttid errters the evaporator through a throttle valve (or a high-resistance thin pipe), where, in the low-pressure chamber, it evaporates and takes on some heat from its environment (e g., from a water jacket), thus it produces chilled water. The vapor then returns to the absorber and is absorbed by the ab-... 

Typically, the generator temperature needed is 80-90°C and chilled water of 8-10°C can be produced. This chilled water is then circulated through an air-to-water heat exchanger (e g., a fan-coil unit) and will cool the air supplied to the rooms. 

The supply pressure can range between 1 and 10 MPa. A first compressor (primary or medium pressure compressor) increases the ethylene pressure to 20-30 MPa. The number of compression steps depends on the pressure of the ethylene which is supplied to the plant. If this pressure is above 3 MPa, the primary compressor typically has two compression stages. Because the ethylene gas is used as a heat sink for the heat generated by the exothermic reaction, the ethylene gas is not totally converted to a polymer in the reactor. The unreacted gas is recycled back into the process. This recycled ethylene is combined with the fresh ethylene at the outlet discharge of the primary compressor. The combined gas streams are fed to the suction of the high pressure compressor. This compressor increases the pressure of the reactor up to 150 - 350 MPa in two steps. The process gas is cooled with cooling water and/or chilled water between the two compression steps. 

High temperature fuel eeUs, like SOFC or MCFC, ean be used both for generating electricity and for tri-gen. Their distinctive feature is relatively high temperature flue gas, which allows heat to be recovered both for the district heating water and chilled water production. An exemplary scheme of such a system is shown in Fig. 5.84. 

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