AUTOFLAME Mk8 MM User Manual

16 Heat Flow
Mk8 MM Manual Page | 288
Calculation Example
A boiler firing at 75% firing rate has a heat input of 20,472,840 BTU/Hr (6MW). The temperature of the flow
(MM temperature detector) is 185°F and the temperature of the return water (T1 temperature sensor) is
167°F. The combustion efficiency is 82% (given by the Mk8 MM). Radiation losses stand at 1% at Maximum
Continuous Rating.
Description
Imperial units
Metric units
Firing rate
75%
75%
Input
20.47 MMBTU/HR
6MW
Return Temperature
167°F
75°C
Flow Temperature
185°F
85°C
Sp Hot water
1.0 BTU/lb/°F
4.18KJ/KG/°C
Density Water
60.68lb/cuft @176°F
972 kg M³ @80°C
Combustion Efficiency
82%
82%
Efficiency % = 100% 18% +
1% × 100
75%

= 80.67%
Useful Heat into Water = Total Heat ×
Efficiency
100
= 20,472,840 ×
80.67
100
= 16,514,440 BTU/hr
Volume Flow in lbs/hr =
16,515,440
1 ×
(
185 167
)
= 917,524.4 lbs/hr
Volume Flow in cu ft Hr =
Volume Flow in lbs hr

Density of Water at Return Temperature
=
917,524.4
60.68
= 15,120.7 cu ft Hr
Volume Flow = 15,120.7 cu ft Hr × 0.124676 = 1,885.2 US GPM
From the above we can see that by enabling Heat Flow Metering expansion function and adding a return
temperature detector to the Mk8 MM, the following information can be obtained:
• Heat input into the water
• Water volume flow

AUTOFLAME Mk8 MM Specifications

General

Brand	AUTOFLAME
Model	Mk8 MM
Category	Controller
Language	English