Thermocouple tent stove temperature

This post is about thermocouple estimation of tent stove temperature. It is has a higher range and is much more accurate than an equally cheap infrared thermometer.

Introduction

The radiant heat from a small backpacking tent stove is the main reason to have stick burning stove in a winter tent.The radiant heat intensity is critically dependant on the surface temperature of the stove.

Radiant heat increases as Temperature⁴. This comes from the Stefan–Boltzmann law. It describes the power radiated from a black body in terms of its temperature in degrees K.

This means that higher stove temperatures will cause enormous increases in the amount of radiant heat that will be provided to campers by their tent stove. This means that radiation increases according to the absolute temperature T⁴ (degrees K multiplied by itself four times). If I have the maths correct, this means that compared with a stove at 300C the same stove at 400C would radiate twice as much heat. It would be three times as much at 500C and 5.3 times at 600C. “These are big and important differences that are largely invisible to us if we cannot reliably measure stove temperature.”

Previously, I have posted on the inaccuracy (100C or more) of tent stove temperature measurements using infrared thermometers. ‘Eyeballing’ temperature from colour charts is similarly inaccurate.

In this post, I describe my early positive experience with the use of a cheap and accurate thermocouple meter with a K-type probe.

A thermocouple or infrared thermometer for tent stove temperature measurement?

It is easy to measures hot stove surfaces with this cheap thermocouple and is much more accurate than an equally cheap infrared thermometer that targets the same hot surface. The thermocouple has a top range of 1300C while most IR thermometers are limited to 600C or less. Temperatures above 600C can be encountered in my tiny and efficient downdraft backpacking tent stoves. A detailed post on these poorer temperature estimating methods is discussed in an earlier post.

Monitoring stove performance by thermocouple tent stove temperature

Static temperature measurement. In another post, I have shown how the thermocouple can easily be fixed mounted to a stove pipe to measure temperatures where tent stove jack material would contact the hot pipe.

My next bit of fun was to find a way of recording the temperatures while tracking over a hot stove surface with the thermocouple probe. I wanted to record the temperature results in a simple way that would be easy to visually share with others and provide the measurements in full context.

Mobile temperature recording. The surface temperatures on all my tent stoves vary considerably. The intense forced-air combustion of a static charcoal bed(1,000C+) combines with the moving and dispersing wood gas flames (800C+). The stove temperatures ebb and flow in their own pulsating but balancing and inexorable dance to their mutual depletion. The sight and sound of this dance to depletion is captured in this little video.

To better understand the path that I have taken to for my temperature measurements it may help to understand some of the inner workings of the stove and how it drives temperature fluctuations. The temperature fluctuations happen as the rough and variable long found fuel sticks feed themselves down, somewhat chaotically, into the inferno of the downdraft inverted stick burner.

The highest temperatures are reached within the static charcoal bed within and below the inverted burner. The turbulent gas flame is less hot, but it spreads its heat widely out over a large portion of the stove cooktop for effective cooking. It also spread heat to the stove wall for comforting radiant heat for the tent occupants.

A dividing wall (or flame guide) between the burner and the stove pipe port, within the stove, makes the flame/hot gas take a long path across the stove. Then the flame/gas turns sharply and turbulently through a notch at the end of the flame guide and back toward the stove pipe. This long and turbulent flame path greatly increases heat for cooking on the stovetop and radiant heat from the stove wall to warm the campers. This long and slow gas combustion path also means that; most of the gas is burnt, less heat is wasted in the stove pipe and no sparks are emitted from the stove pipe.

The temperature recording rig

I made a thermocouple, meter and camera rig that was mounted on a bamboo pole. It was arranged so that the probe location and the meter display could be filmed concurrently (The recording rig, less the camera are shown in the video below).

In the following video I recorded temperature measurements over the surfaces of an experimental downdraft tent stove made from a 20L cooking oil drum. The measurement tracking sequences are:

• Across the stovetop from the burner along the front of the hidden flame guide (The hottest part of the cooktop),
• Down the side of the stove (The body warming radiator),
• Down the side of the stove stand (The insulating support for the stove),
• Back across the stovetop, behind the flame guide to the stove pipe exhaust port (Simmering part of the cooktop),
• Up along the stove pipe.

The measurements up the flue pipe went well enough, but the sunlight angle made the readings invisible on the video recording. “Still not bad for a first try and I will have to do try another approach with the stove pipe.”

Conclusion

A k-type thermocouple and meter makes an excellent and cheap way of measuring the all important temperatures on the surface an ultralight tent stove. It makes a much more accurate measurement tool than an infrared thermometer. The measurement will not be affected by the emissivity of the stove surface as is the case with an infrared thermometer.

Tim