Formula For Calculating Indicated Horsepower

Indicated Horsepower Formula:

\[ IHP = \frac{P1 \times V1 \times \ln(P2/P1)}{33000 \times Eff} \]

P1 (Initial Pressure):

psia

V1 (Volume):

ft³

P2 (Final Pressure):

psia

Eff (Efficiency):

decimal

Indicated Horsepower (IHP):

Unit Converter ▲

Unit Converter ▼

From:	To:

1. What is Indicated Horsepower?

Indicated Horsepower (IHP) is the theoretical power developed within the cylinder of an engine or compressor, calculated from indicator diagrams. It represents the power developed by the working fluid before accounting for mechanical losses.

2. How Does the Calculator Work?

The calculator uses the indicated horsepower formula:

\[ IHP = \frac{P1 \times V1 \times \ln(P2/P1)}{33000 \times Eff} \]

Where:

\( IHP \) — Indicated Horsepower (horsepower)
\( P1 \) — Initial pressure (psia)
\( V1 \) — Volume (ft³)
\( P2 \) — Final pressure (psia)
\( Eff \) — Efficiency (decimal)
33000 — Conversion factor (ft-lb/min to horsepower)

Explanation: This formula calculates the indicated horsepower for compressors by considering the work done during the compression process and accounting for system efficiency.

3. Importance of IHP Calculation

Details: Calculating indicated horsepower is essential for compressor selection, performance analysis, energy efficiency assessment, and proper sizing of compression equipment in industrial applications.

4. Using the Calculator

Tips: Enter initial pressure (P1) and final pressure (P2) in psia, volume (V1) in cubic feet, and efficiency as a decimal between 0 and 1. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is the difference between IHP and BHP?
A: Indicated Horsepower (IHP) is the theoretical power developed in the cylinder, while Brake Horsepower (BHP) is the actual power delivered at the output shaft after accounting for mechanical losses.

Q2: Why is the natural logarithm used in the formula?
A: The natural logarithm accounts for the polytropic nature of the compression process and the relationship between pressure ratios and work done.

Q3: What is a typical efficiency range for compressors?
A: Compressor efficiency typically ranges from 0.7 to 0.9 (70% to 90%), depending on the compressor type, size, and operating conditions.

Q4: Can this formula be used for all types of compressors?
A: This formula is primarily used for reciprocating compressors. Other compressor types may require different calculation methods.

Q5: What are the units for the conversion factor 33000?
A: The factor 33000 converts foot-pounds per minute to horsepower (1 horsepower = 33000 ft-lb/min).