Heat balance - a comparison between the useful heat used to generate steam or hot water, heat losses and the total amount of heat received by the furnace.
Types of heat balance boiler
1, a direct balance equation establishes a relationship between fuel consumption and heat output of the boiler.
This necessarily parameters are measured and the amount of generated steam or water.
2, the reverse of the heat balance equation establishes a relationship between the efficiency of the boiler and heat losses (values are expressed as a percentage).
Heat balance components for analysisthe processes taking place in the furnace boiler for combustion of fuel, in order to: identify the causes of performance degradation to the / a- develop actions needed to improve efficiency.
Components of heat balance
The heat balance of the boiler can be written asequality Q = Q1 + Q2 + Q3 + Q4 + Q5, where Q - is the total amount of heat received by the furnace. It consists of fuel combustion heat, its sensible heat and the heat released to the furnace and the steam supplied to the combustion air: Q = Q H + + Qf.t Qf.v + Qpar.
Qn - net calorific value of the fuel combustion, which is released by the complete combustion without considering the heat of condensation of water vapor.
Qf.t - physical heat fuel counted provided heating fuel before entering the furnace.
Qf.v - warm air introduced into the furnace, is taken into account in the case when the boiler installed heaters.
Qpar - heat steam released to the furnace.
The right side of the equation is the amount of heat consumed in the production of steam or water (Q1) and heat losses (Q2 + Q3 + Q4 + Q5)
Q1 - useful heat is used, time spent on the production of steam or hot water.
Q2 - the heat loss from the exhaust gases (the mostlarge in size, reaching for modern boilers 4-10%. Their size depends on the type of fuel used, to the load / unit, temperature and volume of exhaust gases, and significantly increases with increasing amount of air supplied to combustion).
Q3 - heat loss from the chemical incompletenesscombustion (increases with decreasing supply of air for combustion, moreover, depend on the type of fuel combusted, its mode of combustion, furnace design and other factors).
Q4 - heat loss from physical incomplete combustion of fuel (only when working on solid fuel).
Q5 - heat losses to the environment (dependent onthe quality and thickness of the lining of the boiler, the thermal conductivity of its material on the outside temperature, area, etc.). Calculated in approximate formulas.
The heat balance is established atthe boiler, expressed in kJ / kg (kJ / m3) and usually refers to a 1m3 gas or 1 kg of solid and liquid fuel present at T = 0 ° C and P = 760 mmHg. Art. (0.1 MPa).
return balance equation
It is used mainly for boiler testing. When this value is calculated thermal loss and the known heat of combustion efficiency of the boiler is determined by gross: br = 100 - (Q2 + Q3 + Q5)?.
Errors in determining heat loss lower than when calculating the fuel consumption, so the method determining the reverse efficiency is more accurate balance.