[Stoves] temperature loss during RHC (retained heat cooking)

[Boll, Martin Dr.]

Dear Crispin,

Beste Frans,

 

-First of all a language/abbreviation question: Is RHC =Retained Heat
Cooking, or is it Retained Heat Cooker. I estimate both possibilities are
right.-

 

The temperature loss is the point, which made me think of changing, I will
describe in another posting. First I thought only about thermal loss by
radiation into surrounding. But Crispin, you are clearly right with the slow
heat transition into the food, which already reminded Frans to me, some
months ago.

My first thought being not exactly right, tends into the same desired
direction. There is no difference where the heat goes/escapes. We need a
plus of heat by time, otherwise even the “low-cooking-temperature” (assume
80°C) will not be held.

 

Here we come to Frans. You make cooking experiments in your Duwar-pot. Once
heated op, there is nearly no heat-escape. 

Frans within your Duwar-pot you can exactly describe, how heat goes into the
food, by measuring the temperature of surrounding water. (by known
quantities of water and say: potatoes) during the time.

By knowing this curve, one can possibly describe during what time x the
potatoes need what energy y to hold the temperature  at the same level or
within a certain space (say: 80°C up to 95°C). When we need not to have
exactly the same temperature, we can admit for a time the same amount of
added energy per time, to keep the temperature-range. I assume with current
time it is needed a smaller amount of energy for the time-unit.

Possibly we can give from time to time “a coup de chaleur” (a knock of heat)
like French cooks like to do at the end of their creations. And by that

 – temperature-meeting under control- we can “easily” get a simple scheme
how we must admit heat for cooking economically.

 

For practical ease I propose to do the same thing with simply a
pressure-cooker. There the temperature range for cooking is greater, because
degrees more than 100°C are possible, and as well using temperatures above
100°C shorten cooking time. I will tell you about my first experiences with
my “dressed” pressure cooker”, which made normal eatable potatoes, without
all scientific “Schnickschnack” (I must not translate, because you know the
meaning and the others will find by Leo.org)

 

Frans, for academically reasons one needs the temperature-curve. But for the
practice, only your decision of “eatable” of “not eatable” by what power in
what time, is important to give a hint for other installations/tests,
because all the other RHCs (retained heat cooker) are less good isolated,
and need more power.

 

Regards

Beste groeten

 

Martin

 

P.S. We can be happy when our wrong guesses lead to a possible right way.

 

The previous stoves-list message below was reporting under other topic, but
lead to new topic.

 

Message: 6

Date: Tue, 12 Sep 2006 10:25:06 -0400

From: "Crispin Pemberton-Pigott" <crispin at newdawn.sz>

Subject: Re: [Stoves] Which technologies will best reduce CO and

      blackcarbon,      improve health and safety and lower household energy

      costs?

To: "Stoves" <stoves at listserv.repp.org>

Message-ID: <00b501c6d677$405a2660$6501a8c0 at Averatec>

Content-Type: text/plain;    charset="iso-8859-1"

 

Dear Martin

 

>If fire is speeded up quickly, heat transfer is good and there is no 

>need to reach the boiling point.

 

The problem with speeding up the boiling is that the food itself does not
get hot if the water is rapidly boiled, and it has to be held at the boiling
point to allow the heat to get into the centre of the food.

 

As the RTC can only hold what heat is already in the pot, the temperature of
the (usually dense) food is low, the _average_ temperature of the water+food
is not really near boiling and it will not cook properly.

 

Normally the advice is to cook for 1/3 of the usual time before transferring
to an RTC.  This is to allow the heat to penetrate the food adequately.

 

Even if the boiling were instantaneous, it would still have to be held at
that temperature for a while as the heat is absorbed into the food.

 

Regards

Crispin