Heat Transfer

I recently discovered these aluminum cookpots with stubby rods welded to the bottom to act as fins. These should improve heat transfer to the cookpot.

http://stores.cajunrocketpot.com/-strse-Cajun-Rocket-Stock-Pots/Categori...

Cajun Rocket Stock Pots
4 mm Aluminum Professional Cookware. All our stock pots come with lids. Great for reducing, cooking, frying & boiling stocks, soups, gumbos, potatoes, seafood, pasta, ... Reduces cooktime and fuel usage, saving you time & money. Abosrbs more energy from your burner & distributes that energy more evenly throughout the cooking process. Length dimensions include handles

Has anyone experimented with using a bundt shaped pan for improved heat transfer? It is an open topped donut shaped pan usually used for baking cakes. It would have more surface area for better heat transfer.

Dale Andreatta, Ph.D., P.E. and Alex Wohlgemuth, January 2010

An Investigation of Skirts

Predicted heat transfer to various surfaces of the pot with a 10mm steel skirtPredicted heat transfer to various surfaces of the pot with a 10mm steel skirt

Finned Pots as a Means of Increasing Efficiency Dale Andreatta, Ph.D., P.E., dandreatta@sealimited.com, February 13, 2009

Finned PotFinned Pot

Executive Summary A pot with heat transfer fins has much greater surface area than pots with no fins. In theory, this could lead to greatly increased heat transfer to the pot for a given stove, and the pot would theoretically improve the performance of the stove under all conditions. While we often concentrate on the stove as the primary element of a cooking system, the efficiency of a stove is mainly determined by the heat transfer to the pot, and designing a better pot would be an easy way to make a more efficient stove. A variety of types of finned pots were built and tested. The best designs were separated out in the lab, using natural gas to simulate a wood flame. Several types of fins can be retrofit to existing pots. The better designs of finned pots performed well over a range of conditions using simulated stoves, and sometimes also with an actual wood burning stove modified to use natural gas to simulate a wood flame. With fins on or near the bottom of the pot the finned pots typically gave around a 1.76-fold improvement in heat transfer. If the fins were on the sides of the pot a greater than 2-fold improvement was achieved. Tests on actual stoves using wood as the fuel generally gave smaller improvements in performance, generally 1.33 or less, corresponding to a 25% or smaller reduction in fuel usage. These tests were done under a variety of conditions with a variety of stoves, including the open fire (3-stone fire). On industrial fuel stoves using kerosene or alcohol, improvements were even less, with the finned pots giving 1.2 fold improvements or smaller. In some tests the finned pot used more fuel than an unfinned pot. The reasons for this wide range of results is not known. It is not recommended that finned pots be pursued as a means of increasing the efficiency of stoves. Better results can probably be achieved with less effort by using skirts around the pot. These skirts could be attached to the pots with optimum dimensions. See attached report presented to ETHOS 2009

Dale Andreatta dandreatta@SEAlimited.com November 14, 2004, Updated January 17, 2005

Executive Summary

Dale Andreatta, April 30, 2003

Background and overview

Recently, success has been achieved in making insulative bricks for stoves. My work here seeks to answer the following questions:

  1. What are the thermal properties of these bricks? The properties of interest are density, specific heat, and thermal conductivity.

Big Improvements For Small Cooking Stoves: The Benefits of Heat Recycling
Crispin Pemberton-Pigott, New Dawn Engineering, January 2004

ETHOS CONFERENCE 31 Jan to 1 Feb 2004

These days so much is known about combustion that efficient and nearly complete
combustion can be basically taken for granted, even if the knowledge has not been put into
practice. Combustion geeks now focus to making incremental improvements in the removal
of unwanted combustion products, largely PICs and CO.

Heat Flux Report January 2006, Dale Andreatta, January 2006

Introduction
Omega Engineering makes a small heat flux sensor, a thin device about 25 mm by 25 mm
with 40 embedded thermocouples, which puts out a voltage proportional to the heat flux
through the device. This device was used to perform a series of experiments designed to
begin to answer the following questions:

  1. In a cooking pot that is being heated, where does the heat enter the pot, the bottom
  2. center, bottom edges, the sides, or uniformly?
  3. How much of the heat is transferred through radiation vs. how much of the heat is
  4. transferred through convection?
  5. Can one measure the temperature distributions in the gas around the pot, and can
  6. anything be learned about the heat transfer from these temperature distributions?
  7. Can the heat flux sensor be used to determine the effectiveness of skirts?

Heat flux is defined as heat flow per unit area, and the units are Watts/m2. Another
concept is heat flow, which is the total amount of heat being moved, in Watts. Heat flow
is the integral of the heat flux over the total area, or in other words, the average heat flux times the total area.
In science, it is often useful to compare the conclusions and results with conclusions
drawn from other measurements. If the measurements are consistent, this gives us
confidence that the measurements are accurate. If the measurements are not consistent,
the results may be reported, but the inconsistencies must also be pointed out. In this
report, a rigorous effort will be made to find inconsistencies, both within the data that
was measured, and in comparison with other data that was previously measured.

For more detail, see the attached report:
http://www.bioenergylists.org/files/Heat_Flux_Report_January_2006.pdf

Subscribe to Heat Transfer