Chilled water

Two chillers (300-ton capacity each) provide Chilled Water for various air handling units and all machinery in need of chilled water. Another chiller (15-ton capacity) provides chilled water to boiler, compressor, and deionized water plant. 

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Chilled water lines (refrigeration system or well)... 

A.nnual energy and fuel costs electric energy costs chiller or compressor pumps chilled water heating water condenser or tower water weE water... 

Fig. 38. Caustic purification system a, 50% caustic feed tank b, 50% caustic feed pumps c, caustic feed preheater d, amonia feed pumps e, ammonia feed preheater f, extractor g, trim heater h, ammonia subcooler i, stripper condenser j, anhydrous ammonia storage tank k, primary flash tank 1, evaporator reboiler m, evaporator n, caustic product transfer pumps o, purified caustic product cooler p, purified caustic storage tank q, ammonia stripper r, purified caustic transfer pumps t, overheads condenser u, evaporator v, evaporator vacuum pump w, aqueous storage ammonia tank x, ammonia scmbber y, scmbber condenser 2, ammonia recirculating pump aa, ammonia recycle pump. CW stands for chilled water.

In order to vaUdate this concept, an experiment was performed using an ice-water slurry and it was found that a 25% ice slurry had a two-to-four-times higher thermal capacity than chilled water (44). As the concentration of ice particles in the ice-slurry mixture increased up to 30%, no significant change of pressure drop was reported compared to pure water. 

Polyethylene. This is essentially a closed-ceU insulation manufactured at 448 2 K by an extmsion process. A blowing agent and nucleating agent are employed to control the ceU size, and primary use is in insulating pipelines for hot and chilled water lines, air conditioning, and processing systems. 

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. 

Ejector (steam-jet) refrigeration systems are used for similar apph-cations, when chilled water-outlet temperature is relatively high, when relatively cool condensing water and cheap steam at 7 bar are available, and for similar high duties (0.3-5 MW). Even though these systems usually have low first and maintenance costs, there are not many steam-jet systems running. 

Evaporator is the heat exchanger where refrigerant (water) evaporates (being sprayed over the tubes) due to low pressure in the vessel. Evaporation chills water flow inside the tubes that bring heat from the external system to be cooled. 

Enabhng the use of hard or even sea water for heat rejection e,g, for absorption of gases (CO9, SO9, CIO9, , , ) in chilled water (desorption is provided simultaniously with chilling) when a direct contact barometric condenser is used. 

Factors Affecting Capacity Ejec tor (steam-jet) units become attractive when cooling relatively high-temperature chilled water with a source of about 7 bar gauge waste steam and relatively cool condensing water. The fac tors involved with steam-jet capacity include the following ... 

Chilled-water temperature. As the chilled-water outlet temperature decreases, the ratio of steam/refrigeration effect decreases, thus increasing condensing temperatures and/or increasing the con-densing-water requirements. 

Capacity Control The simplest way to regulate the capacity of most steam vacuum refrigeration systems is to furnish several primary boosters in parallel and operate only those required to handle the heat load. It is not uncommon to have as many as four main boosters on larger units for capacity variation. A simple automatic on-off type of control may be used for this purpose. By sensing the chilled-water temperature leaving the flash tank, a controller can turn steam on and off to each ejector as required. 

The thermocycle system can be operated only when condensing water is available at a temperature lower than the required chilled-water-supply temperature. Modifications for a centrifugal refrigeration unit include the installation of a small liqmd-refrigerant pump, cooler spray header nozzles, and a vapor bypass line between the cooler and the condenser. Without the compressor operating, a thermocycle capacity up to 35 percent of the refrigeration-unit rating can be produced. 

Thermocycle capacity is a function of the temperature difference between the chilled-water outlet temperature leaving the cooler and the inlet condenser water. The cycle finally stops when these two temperatures approach each other and there is not sufficient vapor pressure difference to permit flow between the heat exchangers. 

Precise control of the outlet chilled-water temperature does not occur with thermocycle operation. This temperature is dependent on ambient wet-bulb-temperature conditions. Normally, during cold winter days little change occurs in wet-bulb temperatures, so that only slight water-temperature variations may occur. This would not be true of many spring and fall days, when relatively large climatic temperature swings can and do occur. 

Condenser cooling medium Brine Chilled water Tower water Chilled water... 

Stainless steel corrugated plates from a plate-and-frame heat exchanger. Closed chill water cooling loop used to cool continuous caster mold. 

As part of a protective maintenance activity, the chiller was examined by eddy current. An eddy current check revealed no failures. However, when the chiller was returned to service, leakage of chill water was detected. 

Chilled water control valve Internal Chilled water External Atmosphere Unknown... 

Figure 11.28 Cross-sectional schematic of chill water control valve. (Reprinted with permission from Landis Gyr Powers, Inc., Buffalo Grove, Illinois.)...

Use cooling medium that will not cause freezing (e.g., tempered water instead of chilled water)... 

Chilled water circuit Figure 13.49(c) is a How ditigram for the chilled water. 

Figure 13.49(b) Condenser water Figure 13.49(c) Chilled water circuit... 

The chilled water pump will not start unless the condenser water pump is also running. 

The compressor will not start unless the chilled water and condenser water pumps are also running. 

Direct expansion is also possible wherein the refrigerant is used to chill the incoming air directly without the chilled water circuit. Ammonia, which is an excellent refrigerant, is used in this sort of application. Special alarm systems would have to be utilized to detect the loss of the refrigerant into the combustion air and to shut down and evacuate the refrigeration system. 

Example. To produce 20 tons of refrigeration while delivering 50°F chilled water, the steam consumption depends upon the quantity and temperature of the cooling... 

Figure 1. Ib/hr steam per ton of refrigeration (for lOOpsig steam) for 40°F chilled water.

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