Water Circulation Hot Water Boiler

Overview

Engineering reference data for Water Circulation Hot Water Boiler in water systems.

Key Formulas

Hydrostatic Pressure

$P = \rho g h$

Pressure due to water column.

Flow Rate

$Q = A v$

Area × velocity.

Variables

Water Flow Calculation

The relationship between boiler capacity (power), temperature drop, and water flow is governed by the heat transfer equation. For a water-based system, the formula is:

$Q = \dot{m} \cdot c \cdot \Delta T$

Where:

• $Q$ is the heat transfer rate or boiler capacity (e.g., in kW, Btu/h).
• $\dot{m}$ is the mass flow rate of water (e.g., in kg/s, lb/s).
• $c$ is the specific heat capacity of water (approximately $4.18 \, \text{kJ/kg·K}$ or $1 \, \text{Btu/lb·°F}$).
• $\Delta T$ is the temperature drop of the water flow (e.g., in °C or °F).

Rearranging for water flow rate:

$\dot{m} = \frac{Q}{c \cdot \Delta T}$

Unit Conversions

Key unit conversions for boiler capacity and flow:

• $1 \, \text{gal (US)/min} = 6.30888 \times 10^{-5} \, \text{m}^3/\text{s} = 0.0227 \, \text{m}^3/\text{h} = 0.06309 \, \text{dm}^3/\text{s} = 2.228 \times 10^{-3} \, \text{ft}^3/\text{s} = 0.1337 \, \text{ft}^3/\text{min} = 0.8327 \, \text{Imperial gal (UK)/min}$
• $1 \, \text{hp (English horsepower)} = 745.7 \, \text{W} = 0.746 \, \text{kW} = 550 \, \text{ft·lb/s} = 2,545 \, \text{Btu/h}$
• $1 \, \text{Btu/h} = 0.293 \, \text{W}$
• $1 \, \text{kW} = 3,412 \, \text{Btu/h} = 1.341 \, \text{British hp}$

Example

Water flow through a boiler:
A boiler with capacity $50 \, \text{kW}$ increases the temperature of circulated water by $20^\circ\text{C}$. Using the formula with $c = 4.18 \, \text{kJ/kg·K}$:

$\dot{m} = \frac{50 \, \text{kW}}{4.18 \, \text{kJ/kg·K} \cdot 20 \, \text{K}} = \frac{50}{83.6} \, \text{kg/s} \approx 0.6 \, \text{kg/s}$

This result aligns with the provided data. For imperial units, use $c = 1 \, \text{Btu/lb·°F}$ and adjust capacity and temperature units accordingly.

References

• Original Source