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BASING THE EFFECTIVENESS OF UTILIZATION OF SEWAGE
WATER HEAT BASED ON HEAT PUMP DEVICES IN AUTONOMOUS
HEAT SUPPLY
Ismoilov Sherzod Gayratovich
Karshi Engineering Economics Institute, 180100, Karshi, Uzbekistan
Toshmamatov Bobir Mansurovich
Karshi Engineering Economics Institute, 180100, Karshi, Uzbekistan
https://doi.org/10.5281/zenodo.13751529
Abstract.
In the world, there are strong trends in the use of renewable
energy sources in the creation of energy-efficient systems of management of
heat and fuel-energy resources.
In this article, the authors used traditional methods such as technological
parameters of heat pumps, experimental research, thermal engineering and
calculation of the amount of sewage water and heat capacity to calculate the
efficiency of utilization of sewage heat and its use in heat supply systems. As a
result, it was determined that the overall efficiency of the system when heat
pumps are used in autonomous heat supply systems is 4.
Key words:
heat supply systems, energy efficiency, technological
parameters, heat pumps, autonomous heat supply systems.
Introduction.
Taking into account the picture of population growth,
providing the population with quality and reliable energy units is a problem of
human development. The use of energy is a sign of the strength of the scientific,
technical, and economic management of society, which allows it to realize the
level of its ventilation [1-5].
The energy needs of the countries of the world are increasing year by year.
Currently, the development of energy supply and meeting the need for
energy resources is mainly carried out at the expense of coal, oil, gas, and
nuclear energy. The lack of relative reserves of organic resources (except for
coal) now creates the problem of a stable, high-quality, and reliable supply of
energy units to consumers. In particular, there are serious problems related to
heating and hot water supply systems of objects in rural areas heating of
residents’ homes, stable and reliable supply of natural organic fuels (natural gas,
coal), and their savings. It is known that 40-45 percent of the energy produced in
our Republic is spent on heating and lighting buildings. According to experts in
the field, 360-450 kWh of energy is used on average for heating 1 m
2
of buildings
in Uzbekistan, where the climatic conditions are suitable for us, and 160-240
kWh of energy is used in developed countries. indicators increase with the
improvement of the lifestyle of the population. Therefore, in several decrees and
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decisions of the President of the Republic of Uzbekistan, the introduction of
modern energy-efficient and energy-saving technologies, the development of
renewable energy sources, and the provision of environmental stability are
priorities and tasks defined [6-10].
Energy efficiency in heat supply systems through the use of geothermal,
underground heat, and heat pumps in heat supply systems is one of the most
promising innovations and is receiving great attention worldwide.
Methods and materials.
In this article, the authors determined the heat
of sewage water and the technological parameters, quantities and heat
capacities of heat pump devices using traditional methods such as experimental
research, thermal engineering and calculation.
An autonomous heat supply is a system that provides heat for heating and
hot water supply in buildings and structures without connection to centralized
heat sources. The main principles and elements of autonomous heat supply
include the following aspects:
Autonomous energy supply systems for consumers are becoming popular
today.
In autonomous heat and hot water supply systems, the following sources
are the main sources of heat:
Gas boilers: The most common heat source in stand-alone systems. They
can be either wall-mounted or floor-standing.
Solid fuel boilers: Use wood, coal, pellets and other solid fuels. They
require more frequent maintenance, but can be more economical in some cases.
Electric boilers: Easy to install and operate, but can be expensive to
operate when electricity rates are high.
Heat pumps: Use heat from the environment (air, ground, water) for
heating. They have high energy efficiency, but the initial cost can be high. Heat
pumps are devices that transfer heat from one source to another using the
principle of thermal movement. They can effectively heat buildings and hot
water by extracting heat from the environment (air, ground, or water) and
transferring it to the heating system.
Heating systems.
Radiator systems: Radiators transfer heat to the rooms. They can be made
of various materials, such as steel, aluminum or cast iron.
Underfloor heating: Systems that provide an even distribution of heat over
the floor surface. Can be water or electric.
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Convectors and infrared heaters: Offer alternative heating methods that
can be used depending on the requirements and characteristics of the room.
Due to the decrease in the reserves of traditional energy sources all over
the world, it is possible to achieve energy resource savings by using renewable
energy sources and utilizing secondary energy resources, underground heat [10-
15].
Geothermal energy source temperature is 40÷50
℃
, and low-potential
energy sources (underground heat, soil, sewage water heat) cannot be used as
the main heat source in heat supply systems when it drops below 10÷25
℃
. Heat
pump devices can be used to transfer heat from a low-temperature source to a
high-temperature source, which allows to provide the high temperature
required for the heat supply system.
Over the past decade, the installation and use of geothermal energy
sources and geothermal heat pumps in heat supply systems have grown
significantly worldwide, with an annual growth rate of almost 10%. While most
of this growth has occurred in the United States and Europe, interest is
increasing in other countries such as Japan and Turkey [16].
The system of installation of geothermal energy sources and geothermal
heat pumps and their use in heat supply systems is divided into the following
three systems according to the purpose or method of obtaining heat [17-23].
Calculating the energy efficiency of an autonomous heating system that
uses wastewater heat with a heat pump involves several key steps. These steps
help determine how efficiently the system uses wastewater heat for heating and
hot water supply. Here’s how to approach the calculation and algorithm
development:
Results.
Calculation of potential thermal energy of wastewater. The
energy that can be extracted from wastewater is calculated using the formula:
𝑄
𝑤𝑤
= 𝑉
𝑤𝑤
∙ 𝜌
𝑤𝑤
∙ 𝑐
𝑝
∙ ∆𝑡
, kW
(1)
𝑉
𝑤𝑤
— volumetric flow of wastewater (m³/h);
𝜌
𝑤𝑤
— density of
wastewater (kg/m³, for water usually about 1000 kg/m³);
𝑐
𝑝
— specific heat
capacity of wastewater (kJ/(kg °C), for water about 4.18 kJ/(kg °C));
∆𝑡
—
temperature difference between wastewater and the environment (°C).
Calculation of energy obtained from a heat pump.
The energy obtained from a heat pump is determined by the formula:
𝑄
𝑜𝑢𝑡
= 𝜂
𝐶𝑂𝑃
∙ 𝑁
(2)
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𝜂
𝐶𝑂𝑃
−
heat pump efficiency;
𝑁 −
electric energy consumed by the heat
pump (kWh).
The electrical energy consumed by the heat pump can be found from the
equation:
𝑁 =
𝑄
𝑜𝑢𝑡
𝜂
𝐶𝑂𝑃
(3)
We calculate the total heat balance of the system as follows:
We can calculate the total heat balance according to the following
equation:
𝑄
𝑡𝑜𝑡
= 𝑄
𝑤𝑤
(4)
We calculate the energy efficiency of the system using the following
formula:
𝜂
𝑠𝑦𝑠
=
𝑄
𝑜𝑢𝑡
𝑁+𝑁
𝑎𝑢𝑥
(5)
here,
𝑁
𝑎𝑢𝑥
−
auxiliary energy costs (e.g. for pumps or auxiliary systems).
The overall energy efficiency of the system depends on the ambient
temperature, sewage water temperature, COP of the heat pump, and the
temperature difference. The calculation results are shown in Table 1.
Table 1.
Energy efficiency of the system
No Wastewater
temperature,
℃
Outside air
temperature,
℃
Volume of
wastewater,
m
3
/hours
𝑄
𝑤𝑤
,
kW
𝑁
(
𝜂
𝐶𝑂𝑃
=
4)
, kW
𝑁
(
𝜂
𝐶𝑂𝑃
=
5)
, kW
𝜂
𝑠𝑦𝑠
1
20
10
25,6
1070,08 267,52 214,016 4
2
22
10
25,6
1284,096 321,024 256,8192 4
3
23
10
25,6
1391,104 347,776 278,2208 4
4
24
10
25,6
1498,112 374,528 299,6224 4
5
25
10
25,6
1605,12 401,28 321,024 4
6
26
10
25,6
1712,128 428,032 342,4256 4
7
27
10
25,6
1819,136 454,784 363,8272 4
8
28
10
25,6
1926,144 481,536 385,2288 4
9
29
10
25,6
2033,152 508,288 406,6304 4
10 30
10
25,6
2140,16 535,04 428,032 4
11 31
10
25,6
2247,168 561,792 449,4336 4
12 32
10
25,6
2354,176 588,544 470,8352 4
13 33
10
25,6
2461,184 615,296 492,2368 4
14 34
10
25,6
2568,192 642,048 513,6384 4
15 35
10
25,6
2675,2
668,8
535,04
4
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Conclusion.
This algorithm and calculations will help you understand how
efficiently the system uses wastewater heat and evaluate its potential
capabilities and economic benefits.
The ambient temperature is 10
℃
, the amount of sewage water is 25.6
m
3
/hours,
𝑄
𝑤𝑤
and N change due to the temperature change of the sewage
water. In any case sets
𝜂
𝑠𝑦𝑠
= 4
.
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