104
K. V. S. Teja et al.
output of the plant reaches minimum in these months. However, the variation is not
exactly smooth. The increment is very steep and then it remains almost constant for
a few months before it decreases in a similar manner and again remains constant for
a few more months.
In order to study the variation in output parameters, June month is selected here
and studied. There are 4 major parameters that affect the performance of the plant.
1. Hour of the day
2. Collector radius
3. Chimney radius
4. Collector height.
Other parameters like slope of the collector roof, profile of the chimney, wind velocity,
cloud coverage, day of the year etc. also affect the performance. But the main focus
here was the physical parameters like collector radius, chimney radius, chimney
height and hour of the day. Since the calculations were performed for June, day of
the year is not a major factor because the temperature range over one month is not
much.
4 different cases are now created. The aim here is to keep 3 of the above listed
parameters as constants and vary one parameter. For both case 1 and case 2 all
parameters are varied and compared.
7.3.2 Hour of the Day
Using Eq. (7.1), the hourly incident heat flux was calculated for everyday of the year.
Since the maximum heat flux is incident in the month of May and June, the power
output is also highest for these months. All calculations were performed focussing
majorly on the month of June. Using the heat flux, the rise in temperature within the
system was calculated. The variation of temperature at the chimney inlet versus time
of the day can be observed in Fig. 7.2. It shows the variation between case 1 and case
2. Variation not symmetric between forenoon and afternoon for temperature because
the ambient temperature is higher afternoon compared to forenoon even though the
heat flux distribution is symmetric about 12:00 noon.
From Eq. (7.7), velocity at chimney inlet for every hour was calculated for June.
Corresponding power output was calculated. Monthly averaged values of velocity
and power output were calculated. Variation of velocity at chimney inlet and power
output against time of the day can be observed in Fig. 7.3. Power output is proportional
to the cube of velocity. Hence, their trends are similar when varied with time. Start
low at sunrise and reach maximum around midday and then decrease till sunset.
Distribution is almost symmetric between forenoon and afternoon.
The above curves are similar of case 1 and case 2 but efficiency is very different.
This is because the collector efficiency is also accounted in case 2. This can be seen
in Fig. 7.4. Maximum chimney efficiency is observed when ambient temperature is
minimum i.e. at sunrise. But collector efficiency is maximum at 12:00 noon. This
K. V. S. Teja et al.
output of the plant reaches minimum in these months. However, the variation is not
exactly smooth. The increment is very steep and then it remains almost constant for
a few months before it decreases in a similar manner and again remains constant for
a few more months.
In order to study the variation in output parameters, June month is selected here
and studied. There are 4 major parameters that affect the performance of the plant.
1. Hour of the day
2. Collector radius
3. Chimney radius
4. Collector height.
Other parameters like slope of the collector roof, profile of the chimney, wind velocity,
cloud coverage, day of the year etc. also affect the performance. But the main focus
here was the physical parameters like collector radius, chimney radius, chimney
height and hour of the day. Since the calculations were performed for June, day of
the year is not a major factor because the temperature range over one month is not
much.
4 different cases are now created. The aim here is to keep 3 of the above listed
parameters as constants and vary one parameter. For both case 1 and case 2 all
parameters are varied and compared.
7.3.2 Hour of the Day
Using Eq. (7.1), the hourly incident heat flux was calculated for everyday of the year.
Since the maximum heat flux is incident in the month of May and June, the power
output is also highest for these months. All calculations were performed focussing
majorly on the month of June. Using the heat flux, the rise in temperature within the
system was calculated. The variation of temperature at the chimney inlet versus time
of the day can be observed in Fig. 7.2. It shows the variation between case 1 and case
2. Variation not symmetric between forenoon and afternoon for temperature because
the ambient temperature is higher afternoon compared to forenoon even though the
heat flux distribution is symmetric about 12:00 noon.
From Eq. (7.7), velocity at chimney inlet for every hour was calculated for June.
Corresponding power output was calculated. Monthly averaged values of velocity
and power output were calculated. Variation of velocity at chimney inlet and power
output against time of the day can be observed in Fig. 7.3. Power output is proportional
to the cube of velocity. Hence, their trends are similar when varied with time. Start
low at sunrise and reach maximum around midday and then decrease till sunset.
Distribution is almost symmetric between forenoon and afternoon.
The above curves are similar of case 1 and case 2 but efficiency is very different.
This is because the collector efficiency is also accounted in case 2. This can be seen
in Fig. 7.4. Maximum chimney efficiency is observed when ambient temperature is
minimum i.e. at sunrise. But collector efficiency is maximum at 12:00 noon. This