The
primary advantages of indirect heating are:1. The heating media transfers heat evenly.
2. The coil inside wall temperature is lower, reducing the possibility of caking, scaling and plugging which is a common problem in direct heating. Engineering Technology Incorporated offers 4 types of Indirect Heaters:
Water Bath Heater
Engineering Technology's Inc.'s Water Bath Heaters have a
vessel filled with a transfer media of water or glycol/water mixture (see diagram) and the process coil are submerged in the media. the fire tube transfers the heat released by the burner
to the media which then transfers the heat to the process through the process coil. The maximum operating temperature of the water bath heater is 190 degrees F.
Steam Bath Heater
Similar to the Water Bath Heater only the combustion chamber (firetube)
is immersed in the water bath media. The process coil is located above the water level and its enveloped by saturated steam, which transfers the heat to the process coil. Process outlet temperatures to 215 F can be obtained with the Steam Bath
Heater.
Salt Bath Heater
Engineering Technology Inc's. offers a heater that operates at elevated temperatures to 700 degrees F. The Salt Bath Heater is filled with eutectic salt that has a melting temperature of approximately 290 degrees F. High process outlet temperatures
can be attained because the salt does not degrade at elevated temperatures. Salt Bath heater coils can be serpentine or multi-tube as required for high process flow rates and low pressure drops.
HTE (High Thermal Efficiency)
The HTE heater is a forced draft heater that utilizes the
products of combustion as the heat transfer medium. The heat generating section and the heat transfer section are separated. Heat is transferred to an expanded surface area (finned tube coil bundle) by forced convection. The combustion gases are
circulated from the heating section across the coil section and out the stack. The HTE heater typically delivers 80% gross heating efficiency or 90% net heating efficiency. Flame temperatures are reduced by the recirculated combustion gases
eliminating radiant heat transfer. Process outlet temperatures from 800 degrees F to 1,000 degrees F can be obtained with an HTE heater.
Standard sizes for water bath heaters
are shown below. |
Duty. Btu/hr
Absorbed Heat | Vessel Size | | |
18" OD x 5'0" | | 250,000 | 24" OD x
7'6" | | 500,000 | 30" OD x 10'0" | | 750,000 | 36" OD x 12'0" |
| 1,000,000 | 42" OD x 15'0" | | 1,250,000 |
48" OD x 15'0" | | 1,500,000 |
48" OD x 17'6" | | 1,750,000 |
60" OD x 15'0" | | 2,000,000 |
60" OD x 17'6" | | 2,500,000 |
60" OD x 20'0" | | 3,000,000 |
60" OD x 22'6" | | 3,500,000 |
72" OD x 22'6" | | 4,000,000 |
72" OD x 25'0" | | 4,500,000 |
72" OD x 30'0" | | 5,000,000 |
84" OD x 22'6" | | 6,000,000 |
84" OD x 30'0" | | 7,000,000 |
96" OD x 30'0" | | 8,000,000 |
96" OD x 30'0" | | 10,000,000 |
96" OD x 30'0" | | |
