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2.2: The requisite thermodynamic properties of ammonia for the real cycle. in .NET Integrated ANSI/AIM Code 39 in .NET 2.2: The requisite thermodynamic properties of ammonia for the real cycle.




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Table 2.2: The requisite thermodynamic properties of ammonia for the real cycle. using .net vs 2010 tointegrate bar code 39 for asp.net web,windows application What is GS1 DataBar sta te p o int (se e F ig .net vs 2010 Code 39 . 2 .

11 ) 1r 2r 3r 4r 5r 6r 7r sp e c ific e ntha lp y (k J k g 1) 1420.0 1421.8 1745.

7 1471.8 342.5 332.

8 332.8. p re ssure (b a r) 1.902 1.740 13.

89 13.89 13.11 13.

11 2.077. te mp e ra ture ( C ) 20 VS .NET Code 3/9 20 13 6 36 34 32 18. sp e c ific e ntro p y (k J k g 1 K 1) 5.623 5.671 5.

692 4.919 1.267 1.

267 1.3208. COP = h2 r - h7r = 3.36 h3r - h2 r Cooling capacity = h 1 Visual Studio .NET Code 39 Extended h4 = 1089 kJ kg 1. The relatively high fraction of COPCarnot attained by this cycle derives from our not having introduced unduly small finite-rate heat transfer losses in the heat exchangers in this exercise, i.

e., our having implicitly assumed unusually large heat exchangers for common commercial chillers. __________________________________________________________________________.

The condenser heat exchan ger, evaporator heat exchanger and throttler (expansion device) are common to all mechanical chillers. Construction and design details appear in standard texts such as [Stoecker & Jones 1982; Kreider & Rabl 1994]. The type of compressor used is what.

Thermodynamic and Operational Fundamentals distinguishes among the c lasses of mechanical chillers. The particulars of the main compressor categories, as they relate to the the predictive, diagnostic and optimization studies of concern in this book, will now be reviewed briefly. B4.

Reciprocating Chillers Reciprocating chillers (see Figures 2.12 and 2.13) represent the lion s share of installed cooling capacity in the world.

Typically, reciprocating chillers are used for cooling loads ranging from a fraction of a kW up to about 300 kW. Each cylinder has a moving piston and suction and discharge valves. In contrast, centrifugal and screw compressors employ rotating elements.

Reciprocating compressors can be single- or multi-cylinder. When cooling loads below maximum or rated capacity are required, there are two ways in which a reciprocating chiller responds. The range down to around 70% of full capacity can be realized by changing the coolant temperatures, which in turn affect the state of the refrigerant as it enters the compressor, throttler and heat exchangers.

The compressor continues to operate at a fixed number of cycles per second. All cylinders are active (loaded). In this instance, low cooling rates are not linked to slow physical operation.

We emphasize this point at this juncture, because in later chapters we will invoke experimental measurements of reciprocating chillers to demonstrate that at low cooling rates internal losses that stem from processes such as fluid and mechanical friction dominate the performance of real chillers. There is. Fig. 2.12: Photograph of a reciprocating chiller. 31 Cool Thermodynamics Mechanochemistry of Materials Figure 2.13: Photograph o .net framework 39 barcode f a reciprocating compressor with its valve plate and suction valves.

Refrigerant enters through a valve by suction. The valve closes and the piston compresses the refrigerant, until a second valve (on the opposite side of the valve plate) opens to release compressed higher-pressure higher-temperature refrigerant..

no physical inconsistency between this observation and the fact that frictional losses grow rapidly with fluid or mechanical speed. Namely, low cooling rates do not necessarily imply slow compressor speeds. For part-loads below around 70%, cylinders are unloaded, i.

e., rendered passive by leaving their valves open, while not causing a mechanical imbalance on the compressor linkage. The analyses developed in this book relate primarily to achieving part-load by varying coolant temperatures.

In large chiller plants, low part-loads are readily attained by installing several small individual chillers of varying capacities, and turning one or more of those individual units off as needed. This tends to be a more energy-efficient method, although often at a greater capital investment. B5.

Centrifugal chillers For relatively large cooling loads, starting at around 500 kW, centrifugal compressors (Figure 2.14) are the usual choice. The compressor design is akin to a centrifugal pump, with fluid entering at the center of the impeller and compressed to its edge by centrifugal force (Figure 2.

15). Centrifugal compressors are made with only one wheel for low pressure ratios, but are generally multi-stage. Centrifugal chillers are usually built to operate over a narrow range out of coolant temperatures (evaporator coolant outlet temperature Tevap and in condenser coolant inlet temperature Tcond), typically within 2 C, even though they can supply cooling rates well below rated capacity.

The inlet guide vanes in the centrifugal compressor are closed, to differ32.
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