Water loops

The most common type of air preheater on new units is the rotating wheel. On retrofits, heat pipes or hot-water loops are often more cost-effective because of ductwork costs or space limits. 

Fig. 21. Schematic of a pressurized-water-loop reactor coolant system.

Evaluate the integrity of the old cooling water loop piping, and i.Jemily ways to protect against its failure... 

Baum, A., Water chemistry and corrosion in the steam/water loops of nuclear power stations Seillac, France, Mar. 1980 (1980)... 

Increased usage of recycled fiber in combination with system closure and Hydrogen Peroxide (HP) bleaching at moderate temperatures, has developed microbe cultures that are very effective in decomposing (HP). As this problem often comes slowly when the mills are closing their water loops and reuses their wastewater it is sometimes difficult to say when it needs to be treated. 

Measures SH and SI are hydronic water loop systems with water-to-air heat pumps. These systems also offer energy savings over the base case, but have an incremental cost over the base case. Other than the system type, these measures are the same as SE and SF, so either payback period is immediate for similar reasons. 

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

This is a conventional water loop heat pump system using a boiler and cooling tower to maintain the water loop temperature (see Measures S15-S17 in Section 6.2). Since outside air handling unit and other terminal devices like unit heaters, wall fin convectors, etc which are often used with this water loop heat pump system need a different operating water temperature than that of the water loop, a plate heat exchanger is used between the primary heating circuit... 

Distributed water loop heat Central reversing heat pump... 

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 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. 

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. 

Figure 15. Conventional water loop heat pump system...

Figure 16. Conventional water loop heat pump system with fresh air heating by water-to-air heat pump...

Many of the commercially available air-to-water heat pumps have only published operating data in the entering air temperature range above 40 °F. The performance data below 40 °F is readily available for Toyo and Continental units. Capacity and performance data at ambient temperatures below 40 °F are required to be suitable for use in a water loop heat pump system. Commercially available air-to-water heat pumps in the North American market include Continental, Toyo Carrier, Mac Systems and Environmentally Engineered Equipment Inc. 

Figure 19 depicts a water-loop heat pump system where the cooling tower and boiler have been replaced with a ground heat exchanger. This is the most common configuration of ground source heat pump used in commercial buildings. 

To prevent from hydro-chemical clogging the systems should be designed so there is no entrance of air to the ground water loop. Hence, the loop should be perfectly air tight and constantly under pressure. 

The exhaust air of the building is collected in three exhaust air handling units. Indirect evaporative coolers exploit the remaining cooling capacity of the exhaust air and cool the supply air in the dehumidifier via a water loop. This cold recovery makes the system more efficient. Depending on ambient... 

Optimal water management (water loop arrangement), water clarification by sedimentation, flotation or filtration techniques, and recycling of process water for different purposes. 

Strict separation of water loops and countercurrent flow of process water. 

WATER LOOPS TECHNOLOGICAL ASPECTS AND EXPECTED FUTURE DEVELOPMENTS 223... 

Abstract Closing industrial water loops can substantially improve the environmental... 

It is expected that in the very near future, the application of closed water loops will show an intensive growth, strongly supported by the further development of separate treatment technologies such as anaerobic treatment, membrane bioreactors, advanced biofilm processes, membrane separation processes, advanced precipitation processes for recovery of nutrients, selective separation processes for recovery of heavy metals, advanced oxidation processes, selective adsorption processes, advanced processes for demineralisation, and physical/chemical processes which can be applied at elevated temperature. 

The development and implementation of a closed water loop and the choice of the optimal system is in fact a complex problem. In closed water loops, the composition of the wastewater streams may completely differ from the composition of the wastewater of an industry with conventional water supply and wastewater treatment systems. Besides the temperature of the wastewater in a closed loop system may differ from that of conventional systems. And finally, the removal efficiency of a pollutant can also differ strongly from the removal efficiency of the pollutants in case of a conventional wastewater treatment system. 

As already mentioned, in some industrial sectors closed or almost closed water loops are already used, however in general the applications and experiences are still limited . In any given... 

Further incorporation of closed water loops in a broader environmental frame work, such as, for example in an eco-industrial area. 

The aim of this paper is to provide a basis and a tool for designing specific and concrete closed water loops for various industrial production processes wherein several types of process water are used, and wherein several types of wastewater are produced. 

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