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					SCIENCE HOTSPOTS Chulas

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SCIENCE HOTSPOTS
Chulas
The problems with chulas
This is V. Parminder and his wife. They live in a village called Kovilpatti in Southern India. The Parminders live in a simple mud house and all of their cooking is done on a traditional stove called a chula. Unfortunately, there are several problems in using this cooker. For a start, look at the walls just above the cooker, they are very dark. This is from the soot caused as the chula burns. Imagine what that can do to your lungs over a long period of time.

The second problem is that the Parminders live in a very dry area where trees are hard to find. Since wood is the main source of fuel for the chula, they get through a lot of it because it does not burn the fuel very efficiently.

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ApTibet and the improved chula
Aptibet are a charity who try to improve living conditions for Tibetans living in India. They looked at the traditional chula and came to similar conclusions. Here is a page from their website:

Improved Chulas (Cookstoves)

Cooking is one of the most time-consuming activities in Tibetan daily life and kitchen work is often undertaken by women and the elderly. However, continued cooking on a traditional chula (cookstove) has many further drawbacks,
• •

High fuel consumption, leading to excessive deforestation. Low fuel efficiency

Installing a new chula
• •

Fire risk Numerous health impacts.

Severe smoke pollution, meaning that walls and kitchen utensils frequently become blackened. The old stoves were dirty and smoky, often causing severe eye and respiratory disorders: 70% of Tibetan females suffer chronic coughs as a direct result of cooking over smoking flames. The amount of smoke ingested while cooking for three hours is equivalent to smoking 20 packets of cigarettes.

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Case Study:
700 people live in Dolanji, at an altitude of 5,000 feet. The nearest town is 11 miles away. The residents were formerly dependent on fuelwood, but the price was becoming too high for them, as wood became scarce. The aim of ApTibeT's project was to develop a smokeless stove, where the whole family could be involved in its production. The results of the project were that:
• • •

The improved chulas are efficient and clean, and the kitchen, as above, stays free from smoke. Women, who often make the decision to build the new stoves, save time when cooking. The cost reduction means that the money formerly spent on wood can be used for other needs.

As there is less risk of fire, the elderly and blind are safer, as are children. Health among the Tibetans is much improved, as is awareness of the beneficial environmental impact of the new cookstoves.

During the last 10 years, ApTibeT has built over 3,550 smokeless cookstoves in Tibetan settlements. The masons are trained in construction of the chulas, using locally available material.

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Chulas In The News Improved “Chula” helps to save forest
SHIMLA: In this state where a large percentage of the population is still dependent upon forests to meet their fuel requirements, the improved chulah has gone a long way in saving the forests in the area and checking pollution. Technical support units tested the traditional chulah, conducted surveys and sorted out problems before developing the fuel efficient, smokeless improved versions. These were installed by selfemployed workers who were trained by the technical back-up support units.
Note: Indian currency is the Rupee. £1 is approximately 50 Rupees (Rs 50).

of 4,75,000. A variety of "chulahs," including ordinary pot mud ones, portable metallic stove and high altitude metal stove having an efficiency ranging from 21 to 35 per cent, are being used in the state. The programme is not confined to the rural areas as community cook stoves are also being constructed These stoves are being used in police and Army headquarters, schools, temples and the like where there are mass kitchens. In the high altitudes of this state,especially the tribal pockets where space heating is a major problem, improved high altitude 'chulahs' are being used. During the current financial year, over 12,000 "chulahs" have been installed

A daily allowance of Rs 50 and free tool kits were offered as incentives. Each worker was required to install 200 chulahs in a year and for every chulah installed, he would get Rs 30. He was also entitled to Rs 5 per "chulah" for undertaking repair works after the installation. The number of improved chulas installed up to March 1966 has been 5,52,843 against the targeted number

The Times of India News Service: February 1997

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Chulas in the News
Read the article which is from the "Times of India". It is about a programme to improve the traditional "chula" stoves that are widely used in the state of Himachel Pradesh in the north of the country. Use the article and your scientific knowledge to answer the following questions:
1. Write down two ways in which the chulas were improved. 2. The article mentions "high altitude" chulas. What is the problem of trying to burn things at high altitudes? 3. How could the chula be improved to overcome this problem? 4. If burning wood is such a problem, why do you think that people don't just use an electric stove instead? 5. What two substances are always produced when wood is burned? 6. Name one dangerous substance which may be produced by a poorly designed or maintained stove.

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CHULA CONUNDRUM
A type of cooking stove called a chula has been in use in India for centuries. The idea has been handed down from one generation to the next. In all that time, the basic design has remained unchanged. Recently, however Indian scientists have studied the efficiency of the traditional chula and found that they can improve its performance significantly.

Indian Government statistics show that over 150 million homes use chulas and that they have an average efficiency of only 5 – 10%. Between 40 and 60% of all fuel used in chulas is wood and in 1989, 300 million tonnes of firewood were burned in chulas.

A Traditional Chula

One thing which is a problem with the old design of chula is that it burns the fuel slowly and that it makes a lot of smoke. This is because in the traditional chula, the fuel fails to burn completely.

Improved chula with chimney

When a fuel fails to burn completely, it is called incomplete combustion. This occurs because there is not enough oxygen present. Fuels which burn like this have a dirty, sooty flame. This is caused by particles of carbon which should have reacted with oxygen to form carbon dioxide. The other problem with incomplete combustion is that a gas called carbon

monoxide is released. This is a very dangerous gas and can cause
suffocation in a confined space.

Scientists found that by making an extra hole in the side, the flame is

drawn out by convection causing the flame to burn hotter and the fuel to
burn more completely. The problem of smoke has been solved by the addition of a chimney, which draws the smoke up outside the home.

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Answer these questions
1. What is the advantage in making the chula better, who gains in this? 2. What will happen to the flame in the chula if a hole is made in the side and a chimney fitted? 3. What is the name of the process at work here? 4. Why is it better to have more oxygen present in the flame? 5. Why will fitting a chimney make the chula safer to use?

Chula Challenge
An old and a new style chula were set up to each heat one litre of water. The temperature of the water was measured at one minute intervals and the results are shown below. Old Chula Temp
(C)

20 0

25 1

30 2

35 3

42 4

50 5

60 6

70 7

80 8

95 9

Time
(min)

New Chula Temp
(C)

20 0

25 1

30 2

35 3

44 4

55 5

67 6

81 7

95 8

100 9

Time
(min)

1. Plot graphs of these results, showing time along the x-axis. 2. Which chula gets the water hottest in ten minutes? 3. With the new chula, why doesn’t the water increase in temperature from 9 to 10 minutes? 4. With the new chula, how many degrees does the temperature rise each minute? 5. Look at the results for the old chula, how long do you think that it will take to boil the water?

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Further Improvement: A ceramic liner
The other problem with chulas is that the sides get really hot. This can be dangerous since if a child were to touch the side, she or he could be badly burned. The other problem is that if the sides are getting hot, this means that heat is being lost from the fuel that is burning inside. Chulas have traditionally been made from baked mud, which is quite a good insulator but it needs to be very thick and the mud can crack allowing heat to escape that way. Ceramic is a very good insulator and is an excellent material to line the inside of the chula.

Here are some results for the improved chula, plot a graph as before and explain whether you think that there has been an improvement and if so, why.

New chula with ceramic liner

Temp
(C)

20 0

25 1

33 2

42 3

52 4

64 5

77 6

92 7

100 8

100 9

Time
(min)


				
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