Looped water distribution systems

Some water distribution systems are branched, whereas others are looped. The latter type offers more reliability in case of a pipe failure. The hydraulic engineering problem is to compute the steady velocity or flow rate in each pipe and the pressure at each junction node by solving a large set of continuity equations and nonlinear energy equations that characterize the network. The steady solution of a branched network is easily obtained mathematically however, the looped network initially... 

The size of the central heat pump will be smaller when compared to the total installed capacity of heat pumps in the distributed water loop heat pump system. This is because the central heat pump is sized to meet the block load of the entire building. 

The first cost of this system is expected to be higher than the distributed water loop heat pump system. Addition of a central heat pump and separate piping for hot and cold water should result in higher first cost. 

Fig. 7 Purified water storage and distribution system with ambient loop.

Typical systems include a storage tank with sanitization capabilities. Treated water is sent to the tank and then circulated to the points of use in the manufacturing areas and returned in a continuous loop. The circulation loops are normally designed to maintain flows that will inhibit bacterial growth within the distribution systems. The system designer must be aware of the minimum velocity requirements for these systems. Typically, the designer will use a rule of 4-6 fps (feet per second) as a minimum velocity. 

Liquid water and liquid benzene have very small mutual solubilities. Equilibria in the binary water-benzene system were investigated by Tucker, Lane, and Christian as follows. A known amount of distilled water was admitted to an evacuated, thermostatted vessel. Part of the water vaporized to form a vapor phase. Small, precisely measured volumes of liquid benzene were then added incrementally from the sample loop of a hquid-chromatography valve. The benzene distributed itself between the hquid and gaseous phases in the vessel. After each addition, the pressure was read with a precision pressure gauge. From the known amounts of water and benzene and the total pressure, the liquid composition and the partial pressure of the benzene were calculated. The fugacity of the benzene in the vapor phase was calculated from its partial pressure and the second viiial coefficient. 

If chilled water or cooling water is piped to computer-room units within the computer-room space, provide a looped- or grid-type distribution system with extra valved outlets for flexibility. 

Main distribution systems for water, steam, and electric power should be looped, with block valves (or disconnect switches on electric lines) at appropriate points so that, if any part of the system is damaged, supply can be obtained from another source. 

PAFC systems are commercially available from the ONSI Corporation as 200-kW stationary power sources operating on natural gas. The stack cross sec tion is 1 m- (10.8 ft"). It is about 2.5 m (8.2 ft) tall and rated for a 40,000-h life. It is cooled with water/steam in a closed loop with secondary heat exchangers. The photograph of a unit is shown in Fig. 27-66. These systems are intended for on-site power and heat generation for hospitals, hotels, and small businesses. Another apphcation, however, is as dispersed 5- to 10-MW power plants in metropolitan areas. Such units would be located at elec tric utihty distribution centers, bypassing the high-voltage transmission system. The market entiy price of the system is 3000/kW. As production volumes increase, the price is projec ted to dechne to 1000 to 1500/kW. 

From there, the reaction flow either leaves the total system to be quenched or, more commonly, enters the next plate which contains a delay loop, a spiral channel [56]. Leaving that plate, the streams flow to the last structured plate containing a bifurcation-mini mixer unit. The streams are distributed in multiple streams and contacted with a likewise split water stream. This leads to fast dilution, e.g., of a concentrated sulfuric acid stream, and rapidly cools the reaction stream. The reaction is quenched more or less initially. The final plate is unstructured and acts as a cover plate with holes for liquid withdrawal (Figure 4.28). 

DISTRIBUTED WATER LOOP HEAT PUMP (WLHP) SYSTEMS... 

The maintenance is expected to be lower when compared to the conventional distributed water loop systems. A fan coil unit requires less maintenance than a heat pump due to fewer moving parts. 

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