初一英语教学反思
The Water Boiling Test (WBT) Prepared by Rob Bailis, Damon Ogle and Dean Still with input from Kirk R.
Smith and Rufus Edwards
Houhold Energy and Health Programme, Shell Foundation Introduction
This modified version of the well-known Water Boiling Test (WBT) is a simulation of the cooking process that can be performed on most stoves in u throughout the world. While the test is not intended to replace other forms of stove asssment, it is designed to be a simple method by which stoves made in different places and for different cooking applications may be compared by a standardized and replicable protocol.
Fuel savings among urs who have adopted improved stoves can not be predicted from the results of Water Boiling Tests alone. The Kitchen Performance Test included in this booklet is the only way to demonstrate the field performance of an improved stove. However, the WBT offers a picture of stove performance that can be ud during the design process. Data obtained from a few days of testing assists designers to develop better performing stoves, which can then to be tested by cooks in their intended environment. Visr (2003) has shown that by determining thermal efficiency at high and low
power, as is done in this version of the WBT, fuel u can be predicted for various cooking tasks. A more complete discussion of the us of the WBT can be found in Appendix 2.
The WBT developed for the Shell HEH program consists of three phas.
1)In the first pha, the tester begins with the stove at room temperature and
us a pre-weighed bundle of wood to boil a measured quantity of water in
a standard pot. The tester then replaces the boiled water with a fresh pot
of cold water to perform the cond pha of the test.
2)In the cond pha, water is boiled beginning with a hot stove in order to
identify differences in performance between a stove when it is cold and when it is hot.
3)Lastly, the tester again boils a measured amount of water and then, using a
pre-weighed bundle of wood, simmers the water at just below boiling for a measured period of time (45 minutes). The third step simulates the long cooking of legumes or puls that is common through关于气象的谚语
out much of the world. This combination of tests is intended to measure the stove’s performance at both high and low power outputs, which are important indicators of the stove’s ability to conrve fuel.
Rather than report a single number indicating the thermal efficiency of the stove, which alone can not predict stove performance, this test is designed to yield veral numerical indicators including:
自律作文素材o time to boil
o burning rate
o specific fuel consumption
o firepower
o turn-down ratio (ratio of the stove’s high power output to its low power output)
For more information on each indicator, e Appendix 3, which defines each measure and explains how it is calculated.
A direct calculation of thermal efficiency derived from the Water Boiling Test is not a good indicator of the stove’s performance becau it rewards the excess production of steam.Under normal cooking conditions, excess steam production wastes energy becau it reprents energy that is not transferred to the food. Temperatures within the cooking pot do not ri above the boiling point of water regardless of how much steam is produced. Thus, unless steam is required for the cooking process – for example in the steaming of vegetables (FAO, 1983), excess steam production should not be ud to increa indicators of stove performance.
Before starting the tests…
The following five steps should be completed before beginning the actual tests.
1.)Fuel and water should be procured ahead of time. Ensure that there is an
adequate supply of clean water and fuel.. If possible, try to obtain all of the wood from the same source. It should be well-dried and uniform in size. If kindling is to be ud to start the fire, it should also be prepared ahead of time and included in the pre-weighed bundles of fuel.
2.)Perform at least one practice test on each type of stove in order to become
familiar with the testing procedure and with the characteristics of the
stove. This will also provide an indication of how much fuel is required to boil 5 liters of water. As a rough guide, procure at least 20 kg of air-dried fuel for each stove to be tested in order to ensure that there is enough fuel to complete three tests for each stove. Massive multi-pot stoves may require even more fuel.
3.)The practice period is ud to determine the local boiling point of water.
The local boiling point of water is the point at which the temperature no
longer ris, no matter how much heat is applied. This should be
determined by the following procedure:
⇒Put 5 liters of water in the standard pot and bring it to a rolling boil.
Make sure that the stove’s power output is high, and the water is fully
boiling!
⇒Using the same thermometer that will be ud for testing, measure the boiling temperature when the thermometer is positioned in the
center, 5 cm above the pot bottom. You may find that even at full
boil, when the temperature no longer increas, it will still oscillate
veral tenths of a degree above and below the actual boiling point.
⇒The tester should record the temperature over a five minute period at full boil and note the maximum and minimum temperatures obrved
during this period. The maximum and minimum temperatures should
then be averaged and this result recorded as the “local boiling
temperature” on the data and calculation form. (this need only be
done once for your test location). (Plea e note 2).
4.)A full Water Boiling Test requires at least 15 liters of cool water for each
帮妈妈洗碗作文pot being ud. If water is not available in adequate supply, water ud one day may cooled and reud in the next day’s testing, but do not start any tests with water that is significantly above ambient temperature.
5.) Make sure that there is adequate space and sufficient time to conduct the
tests without being disturbed. The tests should occur in a space completely protected from the wind. It will take roughly 2 hours to conduct a full test of a single stove, including fuel preparation and weighing. It will save time if testers prepare enough weighed bundles of fuel to conduct one or more days of testing ahead of time.
Beginning of Testing Procedure
Initial steps: to be done once for each ries of tests
Equipment ud for one Water Boiling Test:
未来的作文o Scale of at least 6kg capacity and1
gram accuracy
o Heat resistant pad to protect scale
o Digital Thermometer,accurate to 1/10 of a degree, with thermocouple probe suitable for immersion in liquids o Small shovel/spatula to remove charcoal from stove
o Wood moisture meter (optional) o Tongs for handling charcoal
o Timer o Dust pan for transferring charcoal
o Standard pot(s) (u other pots if the standard pot does not fit the stove) o Metal tray to hold charcoal for weighing
o Wood fixture for holding TC probe in
water (e diagram in Appendix 1)
o Heat resistant gloves
o At least 15 liters of clean water for each WBT (may be reud with additions to compensate for spills and evaporation if water is scarce) o 3 bundles of air-dried fuelwood each weighing between 1
and 2 kg. More fuel will be needed if the stove being tested is especially inefficient. A very massive earthen stove may also require more fuel for the cold start pha of the test
1.Fill out the first page of the Data and Calculations form. This includes
information about the stove, fuel and test conditions. Number each ries of tests for future reference.
2.Measure each of the following parameters. The should be recorded once
for each ries of tests. Record the measurements on page 1 of the Data and Calculation form.
a)Air temperature.
b)Average dimensions of wood (length x width x height). This is to give a
rough idea of the size of fuel ud for the test. Testers should u
similarly sized wood for every test in order to minimize variation due to fuel differences. Fuel size should be optimized to the stove if the stove
design calls for specific sizes of fuel. Otherwi, testers should u sticks 2-5 cm in diameter (e Note 5 for a discussion of the effects of fuel
wood variation on stove performance).
c)Wood moisture content (% - wet basis): to be determined 1.) By weighing幼儿园小班个人计划
a sample of wet fuel, drying the sample, and weighing it again or 2.) By
using the wood moisture meter included in the testing kit. (See Note 3
and the ction on variables and calculations below for full details of
defining and measuring moisture content). The Data and Calculation
form contains a special worksheet to record and process your
measurements. See the form for a more detailed explanation.
d)Dry weight of standard supplied pot without lid. If more than one pot is
ud, record the dry weight of each pot. If the weights differ, be sure
not to confu the pots as the test proceeds. Do not u pot lids for
this, or any other pha of the WBT (e Note 4). The standard 7-liter pot (supplied with the test equipment) should be ud wherever possible (e notes). If it is not compatible with the stove, u a pot that is
typically ud and note its dimensions in the “comments” ction of the Data and Calculations worksheet.
e)Weight of container to be ud for charcoal.
f)Local boiling point of water determined by using the same digital
thermometer and nsor that will be ud in the testing (e Note 2).
g)If you have access to a camera (not included in standard kit),
photograph the stove. If you don’t have access to a camera, u a tape
measure to record the dimensions of the stove and describe it in the
space provided.
3.Prepare 3 bundles of fuel wood. The should be pre-weighed: one for each
of the three measurement phas of the test. The third bundle should
contain about twice as much wood as the first two bundles. In every ca, the fuel should be relatively uniform in size and shape: split big pieces of wood and avoid using very small pieces (except for kindling, which should also be prepared in advance if necessary). (e Note 5)
4.Once the parameters have been measured and recorded and the fuel is
prepared, proceed with the test.
Pha 1: High Power (Cold Start)
Data recorded in the remaining phas of the test should be recorded on page two of the Data and Calculation form.
1.Prepare the timer, but do not start it until fire has started.
2.Fill each pot with 5 kg (5 liters) of cold clean water. This amount of water
should be determined by placing the pot on the scale and adding water until the total weight of pot and water together is 5 kg more than the weight of
the pot alone. Record the weight of pot and water on the Data and
Calculations Sheet.
(If the stove can not accommodate the standard pot and the pot that is ud can not accommodate 5 kg of water, OR if a multi-pot stove is ud with non-standard pots that can not accommodate 5 kg of water, fill each pot ~2/3 full and record the change in procedure in the comment space. Record the weight of the pot(s) with the water on the Data and Calculation Form.)
3.Using the wooden fixtures, place a thermometer in each pot so that water
temperature may be measured in the center, 5 cm from the bottom. Make sure the digital thermometer is ud in the primary pot. (If there are
additional pots, u the extra thermometers provided in the testing kit.
Record the initial water temperature in each pot and confirm that it does not vary substantially from the ambient temperature.)
4.The stove should be at room temperature. Start the fire in a reproducible
manner according to local practices. Record any starting materials that are ud other than the wood from the first bundle of pre-measured wood (e.g.
奉新县paper or kerone).
5.Once the fire has caught, record the starting time. Throughout the
following “high power” pha of the test, control the fire with the means commonly ud locally to bring the first pot rapidly to a boil without being excessively wasteful of fuel.
6.When the water in the first pot reaches the pre-determined local boiling
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temperature as shown by the digital thermometer, rapidly do the following:
a.Record the time at which the water in the primary pot (Pot # 1) first
reaches the local boiling point of water. Record this temperature for
primary pot as well.
b.Remove all wood from the stove and extinguish the flames (flames can
be extinguished by blowing on the ends of the sticks or placing them in a bucket of ash or sand; do not u water – it will affect the weight of the wood). Knock all loo charcoal from the ends of the wood into the
container for weighing charcoal.
c.Weigh the unburned wood removed from the stove together with the
remaining wood from the pre-weighed bundle. Record result on the Data and Calculation form.
d.For multi-pot stoves, measure the water temperature from each pot (the
primary pot should be at the boiling point). Record the temperatures on the Data and Calculation Form.
