**3. Description of the studied combined system**

In the current study, a vapor compression refrigeration system (VCRS) is used to chill the cooling water used for cooling the air cooler of the above described steam condenser. Hence, **Figure 3** shows a schematic of the studied combined system. The refrigeration cycle is made up of a two-stage compression system (c) and (d) (these are also designated by I and II, respectively); a refrigerant condenser (e); two throttling valves (f) and (h); a flash tank (g) for intercooling and flash gas removal; a liquid-line/suction-line heat exchanger (LLSL-HE) (b); and an evaporator (a), which acts at the same time as a heat exchanger for chilling the cooling water used in the air cooler. In this system, the low-pressure refrigerant leaving the evaporator (a) is heated in the liquid suction heat exchanger (b) as it

*Air Cooling in Steam Plant Condenser Using Refrigeration System for Improving Vacuum Pump… DOI: http://dx.doi.org/10.5772/intechopen.83787*

#### **Figure 3.**

water within the cooling pipes of the cooling air section, so that the temperature of

*A configuration of the modified steam plant condenser. a, normal cooling water in; b, normal cooling water out;*

**Figure 2** illustrates a configuration for the modified steam plant condenser that enables the use of chilled water to lower the temperature of the air cooler section. The cooling water (a) coming from a water body (river, sea, …) or a cooling tower is fed into the header (e) where it is distributed to the most of the cooling water tubes of the condenser. It helps to cool the steam exhausting out of the plant turbine. This cooling water is called here normal cooling water. While being heated up, it exits the cooling tubes into the header (f). The warmer normal cooling water (b) is extracted from the header (f) and pumped back to the water body or the cooling tower. The chilled water (c) is fed to the header (g) and it flows through the cooling tubes of the air cooling part of the steam condenser. This chilled water acts as a coolant for air along with some water vapor collected in the

air cooler. This leads to cooling the mixture of the air and water vapor to a temperature lower than that of the condensate. The temperature of the chilled water is raised as it flows through the cooling tubes due to heat transfer from the mixture of air and steam in the air cooler. As a result, some of the steam contained in the mixture is condensed and flows down the condenser to the hot well. The warm chilled water goes into the header (h), from which it is transmitted backward to a chiller. Finally, the rest of the air and water vapor mixture in the air cooler is sucked by a vacuum pump and expelled into the atmosphere. The vacuum

In the current study, a vapor compression refrigeration system (VCRS) is used to chill the cooling water used for cooling the air cooler of the above described steam condenser. Hence, **Figure 3** shows a schematic of the studied combined system. The refrigeration cycle is made up of a two-stage compression system (c) and (d) (these are also designated by I and II, respectively); a refrigerant condenser (e); two throttling valves (f) and (h); a flash tank (g) for intercooling and flash gas removal; a liquid-line/suction-line heat exchanger (LLSL-HE) (b); and an evaporator (a), which acts at the same time as a heat exchanger for chilling the cooling water used in the air cooler. In this system, the low-pressure refrigerant leaving the evaporator (a) is heated in the liquid suction heat exchanger (b) as it

the air and accompanying steam is further reduced.

*c, chilled water in; d, chilled water out; e–h, headers.*

*Low-temperature Technologies*

**Figure 2.**

pump is not shown in **Figure 2**.

**226**

**3. Description of the studied combined system**

*A schematic of the combined proposed steam plant condenser and vapor compression refrigeration system. \_\_\_\_\_, water; \_ \_ \_, refrigerant; a, refrigerant evaporator/HE; b, liquid suction HE; c, refrigerant compressor I; d, refrigerant compressor II; e, refrigerant condenser; f, throttle valve I; g, flash chamber; h, throttle valve II.*

absorbs heat from the higher-temperature liquid refrigerant coming from the flash chamber (g). It is drawn by the first-stage compressor (c) where its pressure is raised to the intermediate pressure of the flash chamber. It is sent to the flash chamber (g) in which it is mixed with the refrigerant coming out of the throttle valve (f) and it gets cooled. The refrigerant vapor is separated from the liquid refrigerant and it is drawn by the second-stage compressor (d) and its pressure is elevated to the condenser pressure. The high-pressure refrigerant leaving the compressor (d) flows through the refrigerant condenser (e) where it is condensed and it streams further to the throttle valve (f) where its pressure is reduced to the intermediate pressure of the flash chamber, and it is fed into the flash chamber. The liquid refrigerant leaving the flash chamber is fed to the liquid suction HE (b). Here it is cooled as it gives a portion of its sensible heat to the refrigerant vapor departing the evaporator (a). The cooled liquid refrigerant is reduced in pressure to the evaporator pressure on running through the throttle valve (h). The refrigerant is then run to the evaporator/water chiller to cool down the warm water coming from the air cooler. The low-pressure vapor refrigerant leaving the evaporator/water chiller (a), completes the refrigeration cycle. This refrigeration cycle has been selected among the available refrigeration cycles due to its simplicity and relatively high efficiency.
