Indicated horsepower

Figure 12-6G. AJAX APV-1000, high-efficiency compressor valve. Suction and discharge losses are 4-8% compared to conventional valves with losses of 6-20% as a percentage of the total indicated horsepower. (Used by permission Bui. 2-214. Cooper-...

Mechanical efficiency is the ratio of compressor cylinder indicated horsepower to the brake horsepower. Efficiency values range from 90-93% for direct-driven cylinders to 87-90% for steam engine units. The efficiency of the driver is not included. 

Horsepower is the work done in a cylinder on the gas by the piston connected to the driver during the complete compression cycle. The theoretical horsepower is that required to isen-tropically (adiabatically) compress a gas through a specified pressure range. The indicated horsepower is the actual work of compression developed in the compressor cylinder(s) as determined from an indicator card. Brake horsepower (bhp) is the actual horsepower input at the crankshaft of the compressor drive. It does not include the losses in the driver itself, but is rather the actual net horsepower that the driver must deliver to the compressor crankshaft. 

The mechanical efficiency is the ratio of the indicated horsepower in the compressing cylinders to the brake horsepower delivered to the shaft. It is usually expressed as a percent. 

Steam consumption, pounds per indicated horsepower per hour ... 

Capacities.—If n = number of cylinders, S = piston speed, feet per minute, a = piston area, square inches, pm = mean effective pressure, pounds per square inch, the indicated horsepower of a four-cycle single-acting engine is... 

The mechanical efficiency of a pump is the power utilized in percentage of the power expended. Em — Pump horsepower/Indicated horsepower. Ov Em — Pump horsepower Brake horsepower, in the case of a power pump. It accounts for all mechanical losses in transmitting the power from the power end to the pump end. Table VIII gives usual Em for various types of pumps and different lengths of stroke. 

The indicated horsepower, in the case of a steam pump HPt — HPw/Em> It i determined from indicator cards taken off the steam end. 

Percentage of indicated horsepower lost in friction.per cent... 

Heat units consumed per indicated horsepower-hour.B.t.u. 

Thermal efficiency referred to indicated horsepower [(2546.5 -i-Item 36) X 100]. 

Note.—The items relating to indicator diagrams and indicated horsepower are to... 

The product mix and the production capacities planned for the present and as per planning for the future shall be considered for making a list of the process units and utilities required. The list shall clearly indicate horsepowers (as well as operating voltage, phases, and frequency) and running hours of each motor which will be... 

Typically, the thermal efficiency accounts for only the thermal to mechanical conversion process within the engine. Mechanical efficiency accounts for frictional losses within a heat engine. In an internal combustion engine, the power generated within the engine is known as the indicated horsepower (IHP) and the output power is the brake horsepower (BHP). The two are related by the mechanical efficiency (Hey wood, 1988),... 

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