Horsepower estimating

The vendor should also supply steam consumption data. However, for initial planning the process engineer needs to have an estimate. Use the following equations to calculate the horsepower required to compress noncondensing components from the jet inlet pressure and temperature to the outlet pressure. 

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. 

To assist the engineer in making estimates, the curve in Figure 3-6 gives values of efficiency plotted against pressure ratios. The values on the curve include a 95% mechanical efficiency and a valve velocity of 3,000 feet per minute. Table 3-1 and Table 3-2 are included to permit a correction to be made to the compressor horsepower for specific gravity and low inlet pressure. They are included to help illustrate the influence of these factors to the power required. The application of these factors to... 

Power requirements and discharge temperatures are calculated using the same relationships as used with the other rotary compressors already discussed. The efficiency is. 80 for air service and pressure in the 30 psig range. The mechanical losses are higher than the other rotaries. The mechanical loss is variable and dependent on gas, lubrication, and other factors. For an estimate, use. 15 of the gas horsepower. This approxuna tion should be close enough for an estimate. 

After the type of driven equipment is selected, the horsepower require ments must be estimated. Unless the horsepower requirements happen to fit one of the gas turbine sizes available, a gas engine will be needed. 

A rapid method to estimate pump horsepower is by the following formula ... 

Once the required horsepower and number of stages are estimated, a choice of compressor type can be made from the considerations included earlier. Some example selections are included in Table 10-1, The selections listed in this table are meant as common types that would normally be specified for the given conditions. It must be emphasized that the.se are not recommendations that should be accepted without consideration of the advantages and disadvantages listed earlier. In addition, local foundation conditions, type of drivers available, cost of fuel, availability of spaie... 

Figure 10-11. Curve for estimating compression horsepower. (Reprinted with permission from GPSA Engineering Data Book, lOtb Ed. ...

Kettering and Midgley were the first to identify it as a prime antiknock agent, though the compound had been known since 1852. They estimated that only a veiy small amount of TEL—a few parts per thousand— would result in a 25 percent increase in horsepower as well as fuel efficiency. 

Figure 5-9 indicates the theoretical circulation from a propeller, and Figure 5-10 gives its efficiency for estimating purposes. Efficiency must be used in converting theoretical to actual horsepower, or in converting theoretical to actual circulation of the propeller. 

Usual practice, particularly for good estimating is to assume that the gear drive requires 5% of the impeller horsepower and that system surging or variations require a minimum of 10% of this impeller horsepower. Thus... 

Estimated fan brake horsepower Assume gear drive... 

First, for Figure 14-22, enter at the top at rpm and move to the first estimating turbine wheel diameter then read down to the TSR (calculated or from tables) at Ib/kw-hr read across to base steam rate in Ib/hp-hr. Note that the base steam rate is per hp-hr, and the TSR is per kwh (or kw-hr). Now correct the base steam rate for the horsepower loss (i.e., the portion of blades of turbine spinning outside the nozzle arc, creating friction and windage). From Figure 14-23, at the top read rpm at the exhaust pressure on curved lines noted cond, read down to the estimated wheel diameter, and read the horsepower loss on the left vertical axis. 

Figure 14-23. Horsepower loss in single-stage turbines can be estimated from these curves. (Used by permission Aithearn, F. H. Hydrocarbon Processing, p. 87, Aug. 1979. Guif Pubiishing Co. Aii rights reserved.)...

Exact performance can be given only by the manufacturer for a specified turbine selected to operate at a particular set of conditions. However, estimates can be made which are usually quite satisfactory for general evaluations and comparisons. The most useful criteria are the steam rate and the system cost. Steam rate is the flow of steam in pounds per brake horsepower output per hour through the turbine. It is established for a definite shaft horsepower output, given steam pressure and temperature, exhaust system pressure, and shaft rpm ... 

Bit Hydraulic Horsepower. The effective level of hydraulic energy (hydraulic horsepower per square inch) is the key to optimum bit performance. The rule-of-thumb estimate of diamond bit hydraulic horsepower HPj and penetration rates is shown in Table 4-99. The bit hydraulic horsepower is dependent upon the pressure drop across the bit and the flowrate. 

The higher pressure differentials allow longer and sometimes smaller lines than for fans. To estimate blower horsepower, use Equation 3-4 or 3-5. In lieu of manufacturer s data, use an adiabatic efficiency of 80% for initial work. 

Operation and maintenance charges per year can be related directly to horsepower and are estimated to be between 8.00 and 14.0 /(hp)(year), hence the total operating costs are assumed to be a linear function of compressor horsepower. 

Using data from the SITE demonstration, the total electrical demand for operation of the system was estimated to be about 30 horsepower, primarily to operate the vacuum blower. Assuming continuous operation, electrical costs of 0.06/kWh would result in yearly expenses of about 11,750. It is assumed that the cost of fuel for larger, diesel-operated compressors would be comparable. A small additional cost could be included for lighting the system over night (for security purposes). Including on-site telephone and facsimile service, the total annual utility costs would be about 17,000 per year (D10589F, p. 19). 

Utihties consumption estimate 1200 max installed kilovolt ampere 2200°F afterburner temperature 300 installed horsepower 140 gal/min water usage. 

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