The community heating network’s thermal condition assessment

Heat losses at the heating network’s distribution pipelines were identified for Karkivcommunity. Heat losses’ calculation is performed in view of the underground pipelines’ installationin non-accessible ducts. The heating system water temperature is accepted in line with the heatingnetwork temperature chart and according to the design outdoor temperature value for heatingpurposes. Specific heat losses in the network section’ pipelines are accepted at the level of standardvalues for the specified network laying method. The water flow rate at the heat pipeline sections isdefined as per the design heat loads from the buildings connected to the heat supply network. Theheat pipeline segment with uniform diameter is accepted as the rated section. The soil temperatureat the heat pipeline axis laying depth is accepted as 5°C. The heat losses at the structural networkelements are considered by 1.15 coefficient. The calculations are performed in view of the heatingsystem water flow rate and temperate changes along the heat pipeline length. While analyzing thethermal condition of the return pipelines of the community heating network, the changes in the heatcontent of the heating system water flow in the main direction pipeline during mixing with the waterflow from the branches of the main direction line are taken into account. Considering the averagetemperature of the coldest five days consecutively, the total energy loss in heating pipeline for a groupof buildings in Kharkov region are equivalent to 180.8kW.In view of the ambient air temperature changing over the heating period for Kharkiv cityclimate conditions and the current schedule for quality heat energy supply to the consumers controlthe annual heat losses in the community heating network pipelines were calculated. The soil temperature change at the heat pipeline installation depth during the heating period was notconsidered.Heat losses in the microdistrict network for the year are 2184 GJ. The data obtained can beused to compare options when developing a strategy for reforming the microdistrict heat supplysystem.

Download Full-text

A Distributed Predictive Control of Energy Resources in Radiant Floor Buildings

Journal of Dynamic Systems Measurement and Control ◽

10.1115/1.4043935 ◽

2019 ◽

Vol 141 (10) ◽

Cited By ~ 3

Author(s):

Soroush Rastegarpour ◽

Luca Ferrarini ◽

Foivos Palaiogiannis

Keyword(s):

Energy Storage ◽

Model Predictive Control ◽

Water Flow ◽

Predictive Control ◽

Flow Rate ◽

Thermal Energy ◽

Thermal Energy Storage ◽

Water Flow Rate ◽

Heating System ◽

Energy Resources

This paper studies the impact of using different types of energy storages integrated with a heat pump for energy efficiency in radiant-floor buildings. In particular, the performance of the building energy resources management system is improved through the application of distributed model predictive control (DMPC) to better anticipate the effects of disturbances and real-time pricing together with following the modular structure of the system under control. To this end, the load side and heating system are decoupled through a three-element mixing valve, which enforces a fixed water flow rate in the building pipelines. Hence, the building temperature control is executed by a linear model predictive control, which in turn is able to exchange the building information with the heating system controller. On the contrary, there is a variable action of the mixing valve, which enforces a variable circulated water flow rate within the tank. In this case, the optimization problem is more complex than in literature due to the variable circulation water flow rate within the tank layers, which gives rise to a nonlinear model. Therefore, an adaptive linear model predictive control is designed for the heating system to deal with the system nonlinearity trough a successive linearization method around the current operating point. A battery is also installed as a further storage, in addition to the thermal energy storage, in order to have the option between the charging and discharging of both storages based on the electricity price tariff and the building and thermal energy storage inertia. A qualitative comparative analysis has been also carried out with a rule-based heuristic logic and a centralized model predictive control (CMPC) algorithm. Finally, the proposed control algorithm has been experimentally validated in a well-equipped smart grid research laboratory belonging to the ERIGrid Research Infrastructure, funded by European Union's Horizon 2020 Research and Innovation Programme.

Download Full-text

COMPARISON OF OPTIONS FOR THE HEAT DISTRIBUTION NETWORK OF THE RESIDENTIAL NEIGHBORHOOD

Integrated Technologies and Energy Saving ◽

10.20998/2078-5364.2021.3.02 ◽

2021 ◽

pp. 17-25

Author(s):

O. Aleksakhin ◽

S. Yena ◽

O. Hordiienko ◽

V. Novikov ◽

D. Tsemokh

Keyword(s):

Flow Rate ◽

Distribution Network ◽

Water Flow Rate ◽

Heating System ◽

Heat Losses ◽

Rate Variation ◽

Outdoor Air ◽

Heat Network ◽

Residential Neighborhood ◽

Medium Flow

The comparison of heat losses by pipelines of an extensive residential neighborhood heating system for two options of the distribution network was carried out for a residential neighborhood in Kharkov. The proposed configuration of the heating network differs from the existing ("basic") one in using of the law of heating medium flow rate variation along the heat pipe length. This law takes into account increased flow rate of heating water through branches at the initial sections of the pipeline. The actual flow rate distribution is approximated by a step function. The difference in the laws of flow rate variation is taken into account by the exponent value. The calculation of heat losses was carried out for underground pipelining in non-accessible tunnels. The temperature of heat line water is taken to be the corresponding to the design outdoor air temperature for heating according to the temperature schedule of the heating network. Specific heat losses by pipelines in heat network sections are considered to be at the standard level for non-accessible tunnels. The soil temperature at the depth of the heat pipe axis is taken equal to 5°C. Heat losses by the structural elements of the heat network are taken into account by a factor of 1.15. The variation of the flow rate and temperature of network water in rated pipeline sections is considered in the analysis. The water flow rate at the sections was found based on the design thermal loads of connected buildings. It is shown that when choosing the configuration of the distribution network of the heating system of a group of buildings, preference should be given to the option with a lower value of the exponent in the equation for heating medium flow rate variation along the length of the main line of the network. For extensive heating networks, this can be achieved by connecting as many buildings as possible to the heating network sections close to a heat supply station. An increase in the network water flow rate through the branches at the initial sections of the pipeline ensures a decrease in heat losses by the network pipelines. For the considered part of a residential neighborhood, the decrease in heat loss at the design outdoor air temperature for heating is 5.5 %.

Download Full-text

Heat losses and temperature in the ground under a building with and without ground water flow—I. Infinite ground water flow rate

Building and Environment ◽

10.1016/0360-1323(95)00028-3 ◽

1996 ◽

Vol 31 (1) ◽

pp. 3-11 ◽

Cited By ~ 21

Author(s):

Carl-Eric Hagentoft

Keyword(s):

Ground Water ◽

Water Flow ◽

Flow Rate ◽

Water Flow Rate ◽

Heat Losses ◽

Ground Water Flow

Download Full-text

Heat losses and temperature in the ground under a building with and without ground water flow—II. Finite ground water flow rate

Building and Environment ◽

10.1016/0360-1323(95)00029-1 ◽

1996 ◽

Vol 31 (1) ◽

pp. 13-19 ◽

Cited By ~ 18

Author(s):

Carl-Eric Hagentoft

Keyword(s):

Ground Water ◽

Water Flow ◽

Flow Rate ◽

Water Flow Rate ◽

Heat Losses ◽

Ground Water Flow

Download Full-text

To Combine or Not To Combine An In-Depth Review of Standard and Combined Hydronic Systems and Their Various Pitfalls

Journal of the National Academy of Forensic Engineers ◽

10.51501/jotnafe.v10i2.517 ◽

1993 ◽

Vol 10 (2) ◽

Author(s):

Edward W. Saltzberg

Keyword(s):

Water Flow ◽

Flow Rate ◽

Heat Exchangers ◽

Water Flow Rate ◽

Heating System ◽

Hot Water ◽

Space Heating ◽

System Pressure ◽

Hot Water Supply ◽

Heating Boiler

A hydronic heating system is simply a piping arrangement conveying hot water to heat exchangers in order to provide space heating. A conventional hydronic heating system usually delivers hot supply water at 180 to 200 Fahrenheit temperature and has a dedicated space heating boiler. The hot water return temperature is usually about 140 Fahrenheit, meaning a 40 to 60 temperature difference between supply and return. The conventional hydronic heating system has a relatively constant circulated water flow rate and the temperature of the delivered hot water supply can be reset from outside air temperature. The water flow balancing of a conventional hydronic heating system is somewhat straightforward, although quite critical. The pipe sizing is determined on the basis of gallons per minute flow rate, the selected system pressure drop, and the maximum prudent velocity for the specific piping material. The circulating pump is selected on the basis of the required gallons per minute

Download Full-text

Impact of Water Temperature Changes on Water Loss Monitoring in Large District Heating Systems

Energies ◽

10.3390/en14082060 ◽

2021 ◽

Vol 14 (8) ◽

pp. 2060

Author(s):

Olgierd Niemyjski ◽

Ryszard Zwierzchowski

Keyword(s):

Water Temperature ◽

Water Flow ◽

Flow Rate ◽

Water Flow Rate ◽

District Heating ◽

Heating System ◽

Water Volume ◽

Water Losses ◽

District Heating System ◽

Temperature Changes

This paper explores how water temperature changes in a district heating system (DHS) impact the monitoring of water losses. Water volume in DHS is constantly monitored, recorded, and replenished. The leakage and failure status of the DHS is often monitored through measuring the make-up water flow rate. In this paper, we present the methodology and a simplified model of the dynamics of the heating system operation, which was used to determine the profile of changes in the average temperature and density of water in the system. The mathematical model of the district heating network (DHN) was verified by comparing the results of simulation calculations, i.e., calculated values of the temperature of water returning to the heat source, with the measured values. Fluctuations in water temperature cause changes in the density and volume of water in the DHN, which affect the amount of water supplementing the system. This is particularly noticeable in a DHN with a large water volume. The study reports an analysis of measurement results of operating parameters of a major DHS in Poland (city of Szczecin). Hourly measurements were made of supply and return water temperature, water flow rate, and pressure throughout the whole of 2019. The water volume of the analyzed DHN is almost 42,000 m3 and the changes in water volume per hour are as high as 5 m3/h, representing 20–30% of the value of the make-up water flow rate. The analysis showed that systems for monitoring the tightness of the DHS and detecting failures, on the basis of measurements of the make-up water flow rate, should take into account the dynamics of water volume changes in the DHN.

Download Full-text

Effect of Water Flow on Underwater Wet Welded A36 Steel

Metals ◽

10.3390/met11050682 ◽

2021 ◽

Vol 11 (5) ◽

pp. 682

Author(s):

Eko Surojo ◽

Aziz Harya Gumilang ◽

Triyono Triyono ◽

Aditya Rio Prabowo ◽

Eko Prasetya Budiana ◽

...

Keyword(s):

Mechanical Properties ◽

Water Flow ◽

Flow Rate ◽

Water Flow Rate ◽

Physical And Mechanical Properties ◽

Shielded Metal Arc Welding ◽

Effect Of Water ◽

Bending Effect ◽

Metal Arc Welding ◽

A36 Steel

Underwater wet welding (UWW) combined with the shielded metal arc welding (SMAW) method has proven to be an effective way of permanently joining metals that can be performed in water. This research was conducted to determine the effect of water flow rate on the physical and mechanical properties (tensile, hardness, toughness, and bending effect) of underwater welded bead on A36 steel plate. The control variables used were a welding speed of 4 mm/s, a current of 120 A, electrode E7018 with a diameter of 4 mm, and freshwater. The results show that variations in water flow affected defects, microstructure, and mechanical properties of underwater welds. These defects include spatter, porosity, and undercut, which occur in all underwater welding results. The presence of flow and an increased flow rate causes differences in the microstructure, increased porosity on the weld metal, and undercut on the UWW specimen. An increase in water flow rate causes the acicular ferrite microstructure to appear greater, and the heat-affected zone (HAZ) will form finer grains. The best mechanical properties are achieved by welding with the highest flow rate, with a tensile strength of 534.1 MPa, 3.6% elongation, a Vickers microhardness in the HAZ area of 424 HV, and an impact strength of 1.47 J/mm2.

Download Full-text

Experimental Characterization of a Modified Airlift Pump

Volume 7: Fluids Engineering Systems and Technologies ◽

10.1115/imece2014-39899 ◽

2014 ◽

Author(s):

Afshin Goharzadeh ◽

Keegan Fernandes

Keyword(s):

Water Flow ◽

Flow Rate ◽

High Speed ◽

Water Flow Rate ◽

High Speed Photography ◽

Two Phase ◽

Inner Diameter ◽

Airlift Pump ◽

Flow Map ◽

Churn Flow

This paper presents an experimental investigation on a modified airlift pump. Experiments were undertaken as a function of air-water flow rate for two submergence ratios (ε=0.58 and 0.74), and two different riser geometries (i) straight pipe with a constant inner diameter of 19 mm and (ii) enlarged pipe with a sudden expanded diameter of 19 to 32 mm. These transparent vertical pipes, of 1 m length, were submerged in a transparent rectangular tank (0.45×0.45×1.1 m3). The compressed air was injected into the vertical pipe to lift the water from the reservoir. The flow map regime is established for both configurations and compared with previous studies. The two phase air-water flow structure at the expansion region is experimentally characterized. Pipeline geometry is found to have a significant influence on the output water flow rate. Using high speed photography and electrical conductivity probes, new flow regimes, such as “slug to churn” and “annular to churn” flow, are observed and their influence on the output water flow rate and efficiency are discussed. These experimental results provide fundamental insights into the physics of modified airlift pump.

Download Full-text