Introduction:

As part of our new shop addition, we built a calorimeter room by insulating all 6 surfaces of our new office/testing room.

This will allow direct measurement of heat output, and thus efficency. This will permit calibration of the stack loss method,
which relies on calculations from gas properties in the stack.
The chemical composition of cordwood changes during the batch burn process, necessitating a number of assumptions that have never been fully validated for the specific case of large masonry heaters.

We are changing the combustion air system on the Heat Kit to incorporate some controllable underfire air, to help speed up the charcoal fire at the end of a burn.

We have built a new test heater with a prototype air system.
In addition, we have added several other features for testing:

• Clearances to combustibles
• Heat transfer to the foundation
• Stack loss efficiency
• Particulate emissions
• An experimental low-cost heater facing

Description:

Test corner.
Sheet metal heat shields against the wall, with 1" spacers.
Heater will sit on the piece of cement board shown, which is spaced
off the floor with 1"x1" steel tubing.
Steel tubes sit on sheet metal covered plywood subfloor, which sits on 2" styrofoam, on a concrete slab.

Rear wall detail.
Back facing of heater is replaced with cement board, which is siliconed to the heater facing (see below).
Clearance to heat shield is 4".
This will allow "worst case" clearance to combustible testing with the standard 4" clearance.

Completed heater core.

Chimney connection is visible at the right.
Heater is vented by an 8" i.d. exterior insulated metal chimney.

Chimney connection detail.
A short section of heated bench connects the heater and chimney.
Sliding shut off damper is siliconed in between the two flue liners.
A 1.5" round access port is cored into the left liner, for inserting instrumentation.
Bench is unfaced, for test purposes.
Heater facing will be 2.25" firebricks on edge, with sand/lime slush to the core. Dry test layout is visible.

Combustion Air System:

Sliding damper detail.
Damper will control air to small grate, which sits left-to-right at the rear of the firebox.

Comments and Progress Reports:

Detail of left side facing.
Facing is 2.25" firebrick with 1" mortar slush, 3.5" total thickness.
Fiberglass slip joint is visible.
Heater is located 1" from heat shield.
This will allow a worst case test for clearances.

First fire - January 19/06

Links:

Lopez archive of wood combustion technical information