ISSN: 3030-3931, Impact factor: 7,241
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Original article
739
HYDRAULIC AND THERMAL ANALYSIS OF CLOSED HEAT SUPPLY SYSTEMS
O.Z. Toirov,
E.T. Juraev,
D.O.Hojiev
Tashkent State Technical University, Tashkent, UzbekistanNational Research Institute of
Renewable Energy Sources under the Ministry of Energy, Tashkent, Uzbekistan
Abstract:
This article examines the hydraulic and thermal analysis methods of closed heat
supply systems. Closed systems are widely used in modern thermal infrastructure due to their
energy efficiency, low heat losses, and environmental safety. The hydraulic analysis considers
flow behavior of heat carriers in pipelines, pressure losses, and pump selection. Thermal analysis
addresses heat transfer, temperature regimes, and heat loss evaluation. Mathematical models,
differential equations, and computational algorithms are used to optimize the performance of
closed systems. Studies show that such systems can achieve 10–15% energy savings and ensure
stable operation over their service life.
Keywords:
closed heat supply system, hydraulic analysis, thermal analysis, heat carrier,
pipelines, energy efficiency.
Introduction
Heat supply systems play a crucial role in delivering thermal energy to households, industry, and
the service sector. Traditional open systems discharge the heat carrier (usually water) after use,
resulting in high energy and water losses, and low efficiency.
Closed heat supply systems ensure the recirculation of the cooled heat carrier back to the central
boiler or heat source for reheating. These systems:
- Operate under pressure (typically 3–6 bar)
- Reduce water consumption
- Minimize heat losses
- Simplify hydraulic control
This paper explores in detail the hydraulic and thermal aspects of such systems.
Hydraulic Analysis
Closed heat supply systems typically consist of:
- Heat source (boiler, TPP, renewable source)
- Pipelines (external and internal)
- Pumps (main and auxiliary)
- Thermoregulators and fittings
The primary goal of hydraulic analysis is to ensure adequate pressure difference and flow rate in
the system. Pressure losses are calculated using the Darcy-Weisbach equation:
ΔP = f · (L / D) · (ρ · v² / 2)
Where:
- ΔP: Pressure loss (Pa)
- f: Friction coefficient
- L: Pipe length (m)
ISSN: 3030-3931, Impact factor: 7,241
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Original article
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- D: Pipe diameter (m)
- ρ: Fluid density (kg/m³)
- v: Flow velocity (m/s)
Hydraulic calculations also consider K coefficient, pump head, valve resistances, and opening
levels. Pump selection is based on:
- Total hydraulic losses (static + dynamic)
- Circuit length coverage
- Required flow rate (L/s)
- Operation efficiency and speed
As a result of hydraulic analysis, energy-saving pumps and PID-regulated systems can be
selected.
Thermal Analysis
The basic heat balance equation is:
Q = G · c · (T_in - T_out)
Where:
- Q: Heat flow (W)
- G: Mass flow rate (kg/s)
- c: Specific heat capacity of water (~4200 J/kg·K)
- T_in, T_out: Inlet and outlet water temperatures (°C)
Typical temperature regimes in closed systems:
- 95/70°C (high temperature)
- 75/50°C (medium temperature)
- 55/35°C (low temperature, modern systems)
Systems integrated with solar collectors and heat pumps operate effectively in the 40–60°C range.
Heat loss through pipes is calculated by:
Q_loss = U · A · ΔT
Where:
- U: Heat transfer coefficient (W/m²·K)
- A: Surface area (m²)
- ΔT: Temperature difference (T_pipe – T_ambient)
Modern insulated pipelines reduce losses to 5–7%. Closed systems allow:
- Controlled temperature and pressure
- No vaporization of water
- Reduced corrosion risk
Thermal analysis ensures adequate heat delivery to consumers, optimal return water temperature,
and sufficient backup capacity.
Practical Results
Studies demonstrate that:
- Closed systems save 10–15% more energy than open systems
- Annual water consumption is reduced by 70–80%
- Optimal pump operation reduces electricity use by up to 20%
- Closed systems enhance environmental safety in urban heat supply
Conclusion
ISSN: 3030-3931, Impact factor: 7,241
Volume 8, issue1, Iyun 2025
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Original article
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Closed heat supply systems are among the most efficient, environmentally safe, technically
reliable, and economically viable options. Hydraulic analysis optimizes flow and pressure, while
thermal analysis controls temperature regimes and minimizes heat loss. Well-designed closed
systems increase energy efficiency, extend service life, and reduce thermal energy waste.
Integration with IoT, artificial intelligence, and automated control systems will further enhance
their performance in the future.
References
1. Smirnov, A. & Ivanov, M. (2020). Thermal and Hydraulic Optimization of Closed Heat
Supply Systems. Journal of Thermal Science and Engineering Applications, 12(5), 051009.
2. Müller, H. (2022). Modern District Heating Systems: Closed-loop Hydraulic Design and
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Heating Systems. International Journal of Heat and Mass Transfer, 127, 932–940.
5. IEC 60287-1: Calculation of the Continuous Current Rating of Cables (Standard for Heat Loss
in Insulated Piping Systems).
