As a studio artist, it is often hard to spend large sums of money, even if doing so would pay off in the long run, so glass artist Hugh Jenkins set out to determine just how well he could do with a home-built heat recuperator. After several improvements, he discovered that, depending on how much fuel he used, recuperating hot air in a closed system can reduce fuel consumption by up to 80%. He then applied what he learned when helping a friend build a kiln for ceramics. One of the biggest factors in the performance of these units is a very tight-fitting door. Any gaps can significantly cut the efficiency of the heat exchanger.


This article originally appeared in the December 2007 issue of Ceramics Monthly magazine.
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The recuperator is installed at the top of the stack and consists of a mullite tube that carries the kiln exhaust, surrounded by a metal tube that is several inches larger in diameter than the mullite tube. This forms a cylindrical channel that is open at the top, through which outside air enters the system. The air is heated by the mullite tube and is pulled down into the primary air channels in the brick stack and kiln wall.

The recuperator is installed at the top of the stack and consists of a mullite tube that carries the kiln exhaust, surrounded by a metal tube that is several inches larger in diameter than the mullite tube. This forms a cylindrical channel that is open at the top, through which outside air enters the system. The air is heated by the mullite tube and is pulled down into the primary air channels in the brick stack and kiln wall.

The chimney is a double-wall structure. Flue exhaust travels up the center to the heat exchanger, and heated air from the exchanger travels down the outer chamber to the primary air channels in the back wall of the kiln. Air is drawn through the sytem by compressed air (3) at the bottom of the stack.
The burner blocks are made of castable refractory. The bottom hole is for a pilot burner, and the top houses the main venturi burner. Each fits into the block exactly, so that the only air used is the recuperated, heated air delivered through the primary air channels, which are cast into the blocks. When set into the kiln wall, the vertical channels on the sides of the blocks connect to the channels in the kiln wall. From the vertical channels air enters the burner tube at an angle, creating turbulence in the burner tube, encouraging complete air/gas mixture. Each natural-draft burner has an air control on the back, but they remain closed.

(Click for larger image) Compressed air is introduced into a venturi opening (3) at the base of the recuperation system. This serves not only to pull air into the system from the top of the heat exchanger (1), but also to push the heated air through the channels to the burner blocks (4).

(Click for larger image) Compressed air is introduced into a venturi opening (3) at the base of the recuperation system. This serves not only to pull air into the system from the top of the heat exchanger (1), but also to push the heated air through the channels to the burner blocks (4).

For further information on Hugh Jenkins, see www.bigislandglass.com.

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