Solar industrial Air and Water Systems

The two types of applications employing solar air collectors are the open circuit and the recirculating applications. In the open circuit, heated ambient air is used in industrial applications where, because of contaminants, recirculation of air is not possible. Examples are paint spraying, drying, and supplying fresh air to hospitals. It should be noted that heating outside air is an ideal operation for the collector because it operates very close to ambient temperature, thus more efficiently.

In recirculating air systems, a mixture of recycled air from the dryer and ambient air is supplied to the solar collectors. Solar-heated air supplied to a drying chamber can be applied to a variety of materials, including lumber and food crops. In this case, adequate control of the rate of drying, which can be performed by controlling the temperature and humidity of the supply air, can improve product quality.

Similarly, the two types of applications employing solar water collectors are the once-through systems and the recirculating water heating applications. The latter are exactly similar to domestic water heating systems presented in Chapter 5. Once-through systems are employed in cases where water is used for cleaning in food industries and recycling the used water is not practical because of the contaminants picked up by the water in the cleaning process.

A solar energy system may deliver energy to the load either in series or parallel with the auxiliary heater. In a series arrangement, shown in Figure 7.2, energy is used to pre-heat the load heat transfer fluid, which may be heated more, if necessary, by the auxiliary heater, to reach the required temperature. If the temperature of the fluid in the storage tank is higher than that required by the load, a three-way valve, also called a tempering valve, is used to mix it with cooler make-up or

FIGURE 7.2 Simple industrial process heat system with a series configuration of auxiliary heater.

Three-way valve

Solar Industrial Process Heat

FIGURE 7.2 Simple industrial process heat system with a series configuration of auxiliary heater.

Three-way valve

returning fluid. The parallel configuration is shown in Figure 7.3. Since the energy cannot be delivered to the load at a temperature lower than that of the load temperature, the solar system must be able to produce the required temperature before energy can be delivered.

Therefore, a series configuration is preferred over the parallel one because it provides a lower average collector operating temperature, which leads to higher system efficiency. The parallel feed, however, is common in steam-producing systems, as shown in Figure 7.4, and is explained in the next section.

One of the most important design characteristics to consider when designing a solar industrial process heat system is the time matching of the solar energy source to the load. As was seen in the previous chapter, heating and cooling loads vary from day to day. In industrial process heat systems, however, the loads are pretty much constant and small variations are due to the seasonal variation of the make-up water temperature.

The thermal analysis of air and water solar industrial process heat systems is similar to the analysis presented in Chapter 5 for the solar water heating systems

Solar Industrial Process Heat
FIGURE 7.3 Simple industrial process heat system with a parallel configuration of auxiliary heater.

Steam

Steam

Auxiliary Solar Heating Sytems
FiGURE 7.4 Simple industrial process heat steam system with a parallel configuration with an auxiliary steam boiler.

and will not be repeated here. The main difference is in the determination of the energy required by the load.

Getting Started With Solar

Getting Started With Solar

Do we really want the one thing that gives us its resources unconditionally to suffer even more than it is suffering now? Nature, is a part of our being from the earliest human days. We respect Nature and it gives us its bounty, but in the recent past greedy money hungry corporations have made us all so destructive, so wasteful.

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