2024年5月7日发(作者：源霞辉)

A heating mantle for heating materials,

such as metals, alloys or inorganic

chemicals in a retort, includes a tubular

wall and annular chambers cooperating

with said wall for forming a tortious

path around the retort for hot gases.

The mantle provides a very high

convective heat transfer coefficient.

10 Claims, 2 Drawing Sheets

5,018,707

HEATING FURNACE

BACKGROUND OF THE INVENTION

1. Field of Invention 5 The invention pertains to a gas-fired heating mantle

for heating a retort furnace. This heating mantle provides an improved path for the combustion

gases, thereby raising the rate of heat transfer to the furnace.

2. Description of the Prior Art 10 Gas-fired heating mantles are extensively used in the

metal processing industry for treating and processing metals and alloys, as well as in the inorganic

chemical industry in reactors. However, present mantles are severely deficient in a number of

areas which limits their 15 use in commercial applications. The primary deficiency of present

heating mantles is the limited heat transfer rate from the mantle to the retort.

Typically, a gas-fired heat mantle surrounds a furnace retort vessel, and is constructed to provide a

high rate 20 of heating in a small space. Typically, the mantle is made of a steel shell with an

inside lining of insulating refractory and must be shaped to direct combustion flames away from

the retort vessel to avoid damaging it. In this configuration, heat is transferred to the retort 25

primarily through two mechanisms: one, by convective heat transfer from the combustion gases to

the interior mantle wall and the retort vessel wall; and two, by radiation from the interior mantle

wall to the retort vessel wall. In a gas-fired heating mantle, at tempera- 30 tures below 1200° F.,

the radiation heat transfer rates are low due to lower temperatures, and the convective heat transfer

rates are generally low due to low gas . velocities. This combination results in low overall heat

transfer rates. 35.

At temperatures above 1400° F., heat transfer by radiation from the mantle wall occurs at high

rates, however, the convective rates to the heating mantle wall remain low and becomes the rate

limiting step in the overall heat transfer process. This keeps the overall 40 heat transfer rates low.

Typically, present heating mantles have a heat transfer rate in the range of 5-15 BTU/sq.

ft.-hr.-degree F. depending upon temperature level and gas flow rates.

OBJECTIVES AND SUMMARY OF THE 45

INVENTION

In view of the above disadvantages of the prior art, it is an objective of the present invention to

provide a heating mantle with an improved overall heat rate 50 transfer, in the range of 15-50

BTU/sq. ft.-hr.-degree F., depending upon temperature level and gas flow rates.

The objective is accomplished by providing a heating mantle with an innovative geometric

configuration for 55 improved heat transfer by convection which is the mechanism causing low

heat transfer rates in gas-fired heating mantles.

Other objectives and advantages of this invention shall become apparent from the following

description of 60 the invention. Briefly, a heating mantle constructed in accordance with this

invention, makes use of a baffle arrangement termed "slot-jet configuration." In this configuration,

the overall heat transfer coefficient of the gas-fired heating mantle is increased by increasing the

65 convective coefficient of heat transfer between the combustion gases and the heating mantle as

well as the retort vessel walls. In addition, the mantle wall area for

convective heat transfer, and the overall heating area available for the heat transfer are increased.

This is accomplished by a plurality of axially spaced annular chambers surrounding the retort. The

chambers are formed by suitably shaped baffles and are interconnected by slots for providing a

tortious path for the combustion gases. A substantial pressure drop (approximately one inch water

2024年5月7日发(作者：源霞辉)

A heating mantle for heating materials,

such as metals, alloys or inorganic

chemicals in a retort, includes a tubular

wall and annular chambers cooperating

with said wall for forming a tortious

path around the retort for hot gases.

The mantle provides a very high

convective heat transfer coefficient.

10 Claims, 2 Drawing Sheets

5,018,707

HEATING FURNACE

BACKGROUND OF THE INVENTION

1. Field of Invention 5 The invention pertains to a gas-fired heating mantle

for heating a retort furnace. This heating mantle provides an improved path for the combustion

gases, thereby raising the rate of heat transfer to the furnace.

2. Description of the Prior Art 10 Gas-fired heating mantles are extensively used in the

metal processing industry for treating and processing metals and alloys, as well as in the inorganic

chemical industry in reactors. However, present mantles are severely deficient in a number of

areas which limits their 15 use in commercial applications. The primary deficiency of present

heating mantles is the limited heat transfer rate from the mantle to the retort.

Typically, a gas-fired heat mantle surrounds a furnace retort vessel, and is constructed to provide a

high rate 20 of heating in a small space. Typically, the mantle is made of a steel shell with an

inside lining of insulating refractory and must be shaped to direct combustion flames away from

the retort vessel to avoid damaging it. In this configuration, heat is transferred to the retort 25

primarily through two mechanisms: one, by convective heat transfer from the combustion gases to

the interior mantle wall and the retort vessel wall; and two, by radiation from the interior mantle

wall to the retort vessel wall. In a gas-fired heating mantle, at tempera- 30 tures below 1200° F.,

the radiation heat transfer rates are low due to lower temperatures, and the convective heat transfer

rates are generally low due to low gas . velocities. This combination results in low overall heat

transfer rates. 35.

At temperatures above 1400° F., heat transfer by radiation from the mantle wall occurs at high

rates, however, the convective rates to the heating mantle wall remain low and becomes the rate

limiting step in the overall heat transfer process. This keeps the overall 40 heat transfer rates low.

Typically, present heating mantles have a heat transfer rate in the range of 5-15 BTU/sq.

ft.-hr.-degree F. depending upon temperature level and gas flow rates.

OBJECTIVES AND SUMMARY OF THE 45

INVENTION

In view of the above disadvantages of the prior art, it is an objective of the present invention to

provide a heating mantle with an improved overall heat rate 50 transfer, in the range of 15-50

BTU/sq. ft.-hr.-degree F., depending upon temperature level and gas flow rates.

The objective is accomplished by providing a heating mantle with an innovative geometric

configuration for 55 improved heat transfer by convection which is the mechanism causing low

heat transfer rates in gas-fired heating mantles.

Other objectives and advantages of this invention shall become apparent from the following

description of 60 the invention. Briefly, a heating mantle constructed in accordance with this

invention, makes use of a baffle arrangement termed "slot-jet configuration." In this configuration,

the overall heat transfer coefficient of the gas-fired heating mantle is increased by increasing the

65 convective coefficient of heat transfer between the combustion gases and the heating mantle as

well as the retort vessel walls. In addition, the mantle wall area for

convective heat transfer, and the overall heating area available for the heat transfer are increased.

This is accomplished by a plurality of axially spaced annular chambers surrounding the retort. The

chambers are formed by suitably shaped baffles and are interconnected by slots for providing a

tortious path for the combustion gases. A substantial pressure drop (approximately one inch water