This poster was presented at 2nd International Bose Conference, 2015, December 03-04, 2015, University of Dhaka Abstract Cooling towers use the principle of evaporative cooling to remove process heat from the cooling water and reduces its temperature to the wet-bulb air temperature. It is a heat and mass transfer device. This method of cooling provides with efficient and environment-friendly method of cooling particularly in locations where sufficient cooling water cannot be easily obtained from natural sources or where concern for the environment imposes some limits on the temperature at which cooling water can be returned to the surrounding. Cooling towers are an important part of the nuclear power plants which remove heat from coolant (water) of the condenser and recirculate it. Natural draft cooling towers represent a relatively inexpensive and dependable means of removing heat from cooling water as air inside it is circulated by natural convection, no mechanical means such as fans propellers are needed. The performance of the natural draft cooling tower is dominated by wind speed, ambient air temperatures and humidity in the atmospheric conditions. This paper provides the analysis of designing a natural draft cooling tower considering all these parameters with the help of trial and iterative method. The effect of height, diameter, and the type of filling material selected, are studied.

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In a typical cooling tower water circuit, warm water from the condenser of
the nuclear plant is pumped to the cooling tower, where it is discharged
through a series of sprays against a stream of cooling air. In some cases
one or more propeller fan are used moving air vertically up or horizontally
through the tower. Baffles and fill materials are placed in the path of the
falling water to break it up into tiny drops, thus increasing the effective
surface area of the water. These baffles are made wood, ceramics and in
recent times plastics are used. The tower cools the water by bringing it in
contact with air and evaporating some of the water. The heat lost to the air
which becomes hot and moist by water evaporation. Water in collected in a
reservoir and pumped back to the condenser. Make-up water is added to
the tank to replace the water that is lost die to evaporation, drift and bleed.
ABSTRACT
OBJECTIVES
a) Natural draft cooling
The air circulation through the tower is by natural convection. This type of
towers are made of wood or steel deck. Warm water is discharged at the
top that trickles down across the wooden or metallic decks and into a basin
at the bottom. In spray type towers water is pumped at the top and sprayed
through the nozzles to fall into the basin of the tower.
b) Mechanical Draft Cooling tower
The air circulation of these type of tower is done through by means of
blower or fan. There are type types of mechanical draft cooling towers
namely:
i. Forced Draft Cooling Tower:
Here the fan generates a centrifugal pull using the propeller of the fan that
blows air though the tower, counter to the flow of the water in the tower. A
forced draft cooling tower is compact in size but it requires additional
horsepower and in fact more than the induced one.
ii. Induced Draft Cooling Tower:
In this type of tower the propeller fan is located at the top of the tower and
the air is pulled out of it from the ends through the tower across the water
flow path.
• Reactor thermal output = 3200 MW th
• Power plant output = 1170 MW e
• Power plant output, net = 1082 MW e
• Reactor type: Pressurized Water Reactor (PWR)
VVER - 1000 SPECIFICATIONS SELECTION OF COOLING TOWER FILL
The heart of evaporative cooling is its fill, a packing of sort designed to
provide the necessary contact area and contact time between air and water.
If the fill is in good condition the tower will provide ample amount of
cooling tower at the temperature that is was designed to provide. If not
then it will not provide cool water.
SUMMARY
From the above two table it is clearly depicting that splash type fill would
be the most effective. It is best to consult with cooling tower manufacturer
what type of fill would be best with excellent thermal properties and a
water specialist who can recommend the appropriate treatment chemicals
to minimize deposits.
The authors of this paper have mathematically analyzed the relationship
among different parameters as range, approach, mass flow rate etc. for the
natural draft cooling tower of a rated nuclear power plant. From the
calculation, a 150 m high ND cooling tower has been selected for Ruppur
nuclear power plant (VVER-1000). The figures help to visualize a
generalized analysis of different cooling tower. Further to improve the
performance of heat transfer impacts of various types of fill media were
discussed.
1. To provide an overview of different types of cooling tower used in a
typical nuclear reactor.
2. To design a Natural Draft Cooling Tower for a 1000MW nuclear
reactor.
3. To analyze the cooling tower in different conditions.
4. To select the type of fill media.
BANGLADESH UNIVERSITY OF ENGINEERING & TECHNOLOGY
Sayeed Mohammed, Syeda Noor –E– Lamia, Musanna Galib and M. A. Rashid Sarkar
THERMAL ANALYSIS AND DESIGN OF A NATURAL DRAFT COOLING TOWER OF A 1000 MW
NUCLEAR POWER PLANT
WORKING PRINCIPAL OF COOLING TOWER
Cooling towers use the principle of evaporative cooling to remove process
heat from the cooling water and reduces its temperature to the wet-bulb air
temperature. It is a heat and mass transfer device. This method of cooling
provides with efficient and environment-friendly method of cooling
particularly in locations where sufficient cooling water cannot be easily
obtained from natural sources or where concern for the environment
imposes some limits on the temperature at which cooling water can be
returned to the surrounding. Cooling towers are an important part of the
nuclear power plants which remove heat from coolant (water) of the
condenser and recirculate it. Natural draft cooling towers represent a
relatively inexpensive and dependable means of removing heat from
cooling water as air inside it is circulated by natural convection, no
mechanical means such as fans propellers are needed. The performance of
the natural draft cooling tower is dominated by wind speed, ambient air
temperatures and humidity in the atmospheric conditions. This paper
provides the analysis of designing a natural draft cooling tower considering
all these parameters with the help of trial and iterative method. The effect
of height, diameter, and the type of filling material selected, are studied.
TYPES OF COOLING TOWER
RUPPUR NUCLEAR POWERPLANT
The plant is a proposed 2 GWe nuclear power plant of Bangladesh. It is
proposed to go into operation by 2022 and will be the country's first
nuclear power plant. The nuclear power plant will be built at Ruppur,
200 km north-west of Dhaka, in the Ishwardi sub district of Pabna District,
in the northwest of the country. The proposal was first raised in 1961.
Government took 253.90 acre of land of current place at that year to build
the plant. In 1963 the plant was approved. Discussions took place with the
Canadian government in 1964 and 1966. Discussions with the governments
of Sweden and Norway were also going on in those years. However, no
real progress was achieved. After the independence of Bangladesh, the
Government of Bangladesh started discussion with the Soviet Union in
1974, however no agreement was reached.
In 2009 the Bangladesh government again started discussion with the
Russian government and on 13 February the two governments signed a
MoU. Rosatom said they would start construction by 2013.
In 2013 group of Bangladeshi scientists from Bangladesh and the global
diaspora voiced profound concern over the safety and economic viability
of the plant. Several separate issues were raised, from the unsuitability of
the site to the obsolescence of the VVER-1000 model proposed,
questionable financing arrangements and a lack of agreement with Russia
over nuclear waste disposal.
In 2015 the proposal was delayed by a year. Rosatom also offered a two
VVER-1000 reactor power plant, which would increase output to 2.4 GWe.
TOWER DESIGN
Based on the specifications of Ruppur nuclear reactor a design of natural
draft cooling tower was made using the above equations through iterations
the height of the cooling tower was determined
NAME SYMBOL DESCRIPTION UNITS
Duty
coefficient
𝑫 𝒕
𝑾 𝑳
𝑫 𝒕
= 𝟎. 𝟎𝟎𝟑𝟔𝟗 ∗
∆𝑯′
∆𝑻
∗ (∆𝑻∗ + 𝟎. 𝟎𝟕𝟓𝟐∆𝑯′) 𝟎.𝟓
--
Base area of
tower
𝑨 𝒃 𝑫 𝒕 =
𝟏𝟗. 𝟓 ∗ 𝑨 𝒃 ∗ 𝒛 𝒕
𝟎.𝟓
𝑪 𝒕
𝟏.𝟓
m2
Height of
tower
𝒛 𝒕
Assumed values are used during
calculations to confine to a height to
diameter ratio of 3:2; in case of
hyperbolic natural draft towers
m
Diameter of
tower
𝒅 𝒃 𝒅 𝒃 =
𝟒 ∗ 𝑨 𝒃
𝝅
m
No.
Height
𝒛 𝒕 (m)
𝑨 𝒃 =
𝑫 𝒕 ∗ 𝑪 𝒕
𝟏.𝟓
𝟏𝟗. 𝟓 ∗ 𝒛 𝒕
𝟎.𝟓
(m2)
𝒅 𝒃 =
𝟒 ∗ 𝑨 𝒃
𝝅
(m)
Height to
diameter ratio
𝒛 𝒕 / 𝒅 𝒃 ≈ 1.5
1 150 7321 96.55 1.55 ≠ 1.5
2 145 7446.64 97.37 1.48 ≠ 1.5
3 147 7395.81 97.04 1.51 ≅ 1.5
From the above calculation it is evident that about 150m high natural draft
cooling tower is to be designed to cool a 1000MW nuclear reactor.
Now here the design was made for a particular range. Now for other ranges
we can visualize how the height of the tower changes
There are different types of fill media and each have different capabilities.
Now as an engineer it is a challenge to determine the optimum fill media
based on the design of the cooling tower. So they types of fill that are
available for the design are
Now the above shows us the different types of fill but to choose the best
fill the following two charts will make the selection criteria easier.
REFERENCE
1. Selecting the Optimum Cooling Tower Fill by Paul R. Puckorius.
2. Determination of Optimum Height for Counter Flow Cooling Tower by
Ashraf Kotb.
3. ASHRAE Handbook, “HVAC Systems and Equipment (SI)”, American
Society of Heating, Refrigeration and Air Conditioning Engineers, Inc..
ASHRAE (2008).