Horsepower calculation

The expander equation (Equation 1) is generated from the standard compressor head calculation (see Compressors, Horsepower Calculation) by ... 

If the system differential pressure requirements are low, sometimes a fan can be used. A fan is limited to a maximum of about 65 inches of water (just over 2psi) in vacuum service or 77 inches of water in pressure service (just under 3psi). To estimate fan horsepower use the equations found in Chapter 6 in the section entitled Horsepower Calculation. In lieu of manufacturer s data use an adiabatic efficiency of 50% for initial work. 

Compressor horsepower is best determined using the horsepower calculation in Chapter 6. For refrigeration compressors, the horsepower can he approximated another way that may prove to be simpler. The compressor horsepower per ton of refrigeration load depends upon the evaporator and eondenser temperatures. See the seetion titled Estimating Horsepower per Ton in Chapter 11. 

Example 12-4. Horsepower Calculation Using Mollier Diagram... 

Alternate brake horsepower calculation Using Figure 12-63 for air. 

Most compressor manufacturers use the adiabatic horsepower calculation, Eq. (8.3), which is therefore recommended and applied here. 

TABLE II Hydraulic Horsepower Calculations for Candidate Pipes... 

Manufacturers performance curves, such as those in Fig. 10, contain a great deal of useful information. Actual average head-capacity curves are shown for a number of impeller diameters. Also superimposed on these head curves are curves of constant efficiency. A third set of cur ves superimposed on the head curves are the NPSH requirement curves (dashed line in Fig. 10), which indicate the required NPSH at any given condition of operation. A fourth set of curves sometimes included are the BHP (brake horsepower) curves. BHP is the actual horsepower calculated in the previous HGL method illustration. It is the HHP divided by the effciency. 

Efficiency and Brake Horsepower Calculations for the 6-inch Centrifugal Pump Program Inputs and Outputs... 

With a pull-through drive system, the recoiler horsepower must be the larger of that calculated by Eq. (1) or (6). When the horsepower calculated by Eq. (1)... 

Note that the formulas for flatteners, slitters, and scrap choppers each contain the value thickness squared. The resulting horsepower calculation varies proportionally to the square of the thickness. For example, if the thickness were doubled, the resulting horsepower would be four times greater. For those considering the purchase of a slitting line, the importance of carefully establishing the... 

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