scholarly journals New Dimensionless Correlations for the Evaluation of the Thermal Resistances of a District Heating Twin Pipe System

2021 ◽  
Vol 11 (20) ◽  
pp. 9685
Author(s):  
Massimo Corcione ◽  
Luca Cretara ◽  
Lucia Fontana ◽  
Alessandro Quintino
Keyword(s):  
Thermal Resistance ◽  
Control Volume ◽  
District Heating ◽  
Heat Losses ◽  
Thermal Engineering ◽  
Thermal Conductivity Ratio ◽  
Burial Depth ◽  
Pipe System ◽  
Double Pipe ◽  
Dimensionless Correlations

The heat losses from pre-insulated double-pipe district heating (DH) systems buried in a homogeneous soil are studied numerically. The study is conducted using the diameter of the pipes and their distance, the size of the insulation, the thermal conductivity ratio between the insulation and the soil, as well as the burial depth of the double-pipe system, as controlling parameters. A computational code based on a control-volume formulation of the finite-difference method has been developed using the open-source framework OpenFOAM with the purpose to compute the heat transfer rate across adjacent solid regions with different thermophysical properties. The main scopes of the study are: (a) to investigate in what measure the geometry and the relative position of the warm and cold pipes, as well as the temperature imbalance, the burial depth and the physical properties of both the insulation and the soil, affect the heat losses; (b) to analyze the existence of an optimal configuration of the DH system by the thermal resistance enhancement viewpoint; and (c) to develop accurate correlating equations for the evaluation of the thermal resistance existing between each pipe and its surroundings, useful for practical thermal engineering applications.

scholarly journals The Influence of Burial Depth and Soil Thermal Conductivity on Heat Transfer in Buried CO2 Pipelines for CCS: A Parametric Study

2020 ◽  
Author(s):  
Babafemi Olugunwa ◽  
Julia Race ◽  
Tahsin Tezdogan
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Steady State ◽  
Thermal Resistance ◽  
Parametric Study ◽  
Flow Assurance ◽  
Burial Depth ◽  
Soil Thermal Conductivity ◽  
Dense Phase ◽  
Pipeline Transportation

Abstract Pipeline heat transfer modelling of buried pipelines is integral to the design and operation of onshore pipelines to aid the reduction of flow assurance challenges such as carbon dioxide (CO2) gas hydrate formation during pipeline transportation of dense phase CO2 in carbon capture and storage (CCS) applications. In CO2 pipelines for CCS, there are still challenges and gaps in knowledge in the pipeline transportation of supercritical CO2 due to its unique thermophysical properties as a single, dense phase liquid above its critical point. Although the design and operation of pipelines for bulk fluid transport is well established, the design stage is incomplete without the heat transfer calculations as part of the steady state hydraulic and flow assurance design stages. This paper investigates the steady state heat transfer in a buried onshore dense phase CO2 pipelines analytically using the conduction shape factor and thermal resistance method to evaluate for the heat loss from an uninsulated pipeline. A parametric study that critically analyses the effect of variation in pipeline burial depth and soil thermal conductivity on the heat transfer rate, soil thermal resistance and the overall heat transfer coefficient (OHTC) is investigated. This is done using a one-dimensional heat conduction model at constant temperature of the dense phase CO2 fluid. The results presented show that the influence of soil thermal conductivity and pipeline burial depth on the rate of heat transfer, soil thermal resistance and OHTC is dependent on the average constant ambient temperature in buried dense phase CO2 onshore pipelines. Modelling results show that there are significant effects of the ambient natural convection on the soil temperature distribution which creates a thermal influence region in the soil along the pipeline that cannot be ignored in the steady state modelling and as such should be modelled as a conjugate heat transfer problem during pipeline design.

scholarly journals METHODOLOGY OF THE PRIMARY DATA RECONSTRUCTION OF SINGLE PIPE HEATING SYSTEMS/VIENVAMZDŽIŲ ŠILDYMO SISTEMŲ PIRMINIŲ DUOMENŲ NUSTATYMO METODIKA

1999 ◽  
Vol 5 (5) ◽  
pp. 318-322
Author(s):  
Edvardas Tuomas ◽  
Saulius Neverbickas
Keyword(s):  
World War Ii ◽  
District Heating ◽  
Heating System ◽  
Heat Fluxes ◽  
Primary Data ◽  
Complex Coefficient ◽  
Heating Systems ◽  
Pipe System ◽  
Central Heating ◽  
Single Pipe

The majority of dwellings in Lithuania are situated in blocks of flats. The dwellings were built after World War II and they are heated by single pipe central heating systems, connected to district heating. The dwellers are not quite satisfied with such a heating system and try to improve it, but do that in a wrong way, by increasing the surface of radiators. Such means lead to violation of thermal regime and comfort conditions for other dwellers. There exists sometimes the necessity of reconstructing premises and together—the heating system. During the reconstruction the primary heat fluxes from radiators should be known, but very often such data are lost and only the size of radiators (number of sections) are known. To reconstruct the required primary data for single pipe systems is complicated because the temperatures of inlet and outlet water for radiators are unknown. In this article the methodology is proposed how to perform the calculations leading to the required data. The aim of calculations is the establishment of heat fluxes from each radiator connected to the riser. Heat flux from radiator can be calculated according the formula (1) but the complex coefficient is unknown. It could be found from formulae (2) but some magnitudes are unknown. According to the proposed methodology the values of unknown magnitudes are taken approximately and calculations are performed with iterations. In such a way the flow rate of water in riser is established from formula (3), which is the same for each radiator (the property of single pipe system). From formulas (3) and (4) an equation is produced (5), and is used for calculations of unknown temperatures. The equation (6) is used for calculation of heat fluxes from radiators. To carry out the above-mentioned calculations without computer practically is impossible due to many cycles of iteration. The programme was prepared to make easy all these calculations. The scheme of algorithm of programme is given in Fig 1. An example of calculation is given in this article. Calculations were fulfilled by newly created programme. The riser chosen for calculation is shown in Fig 2. The results of calculation are given in Table 1. The table shows that according to the proposed methodology the programme based on it can be used for reconstruction of primary data of single pipe heating systems successfully.

scholarly journals Investigation of Bath/Freeze Lining Interface Temperature Based on the Rheology of the Slag

JOM ◽  
2021 ◽  
Author(s):  
Samant Nagraj ◽  
Mathias Chintinne ◽  
Muxing Guo ◽  
Bart Blanpain
Keyword(s):  
Thermal Degradation ◽  
Thermal Resistance ◽  
Conceptual Framework ◽  
Batch Process ◽  
Heat Losses ◽  
Interface Temperature ◽  
Freeze Lining ◽  
High Thermal Resistance ◽  
Critical Viscosity ◽  
Physical And Chemical

AbstractFreeze lining is a solidified layer of slag formed on the inner side of a water-cooled pyrometallurgical reactor, which protects the reactor walls from thermal, physical, and chemical attacks. Because of the freeze lining's high thermal resistance, the reactor heat losses strongly depend on the freeze lining thickness. In a batch process such as slag fuming, the conditions change with time, affecting the freeze lining thickness. Determining the freeze lining thickness is challenging as it cannot be measured directly. In this study, a conceptual framework based on the morphology and microstructure of freeze lining and the rheology of the slag is discussed and experimentally evaluated to determine the freeze lining thickness. It was found that the bath/freeze lining interface lies just below critical viscosity temperature. The growth of the freeze lining is primarily controlled by the mechanical and thermal degradation of the crystals forming at the interface. The bath/freeze lining interface temperature for the measured slag lies in the range of 1035–1070°C.

scholarly journals Sensitivity Enhancement of Silicon-on-Insulator CMOS MEMS Thermal Hot-Film Flow Sensors by Minimizing Membrane Conductive Heat Losses

Sensors ◽  
2019 ◽  
Vol 19 (8) ◽  
pp. 1860 ◽  
Author(s):  
Zahid Mehmood ◽  
Ibraheem Haneef ◽  
Syed Zeeshan Ali ◽  
Florin Udrea
Keyword(s):  
Thermal Conductivity ◽  
Thermal Resistance ◽  
Film Flow ◽  
Heat Losses ◽  
Silicon On Insulator ◽  
Conductive Heat ◽  
Circular Membrane ◽  
Flow Sensors ◽  
Cmos Mems ◽  
Hot Film

Minimizing conductive heat losses in Micro-Electro-Mechanical-Systems (MEMS) thermal (hot-film) flow sensors is the key to minimize the sensors’ power consumption and maximize their sensitivity. Through a comprehensive review of literature on MEMS thermal (calorimetric, time of flight, hot-film/hot-film) flow sensors published during the last two decades, we establish that for curtailing conductive heat losses in the sensors, researchers have either used low thermal conductivity substrate materials or, as a more effective solution, created low thermal conductivity membranes under the heaters/hot-films. However, no systematic experimental study exists that investigates the effect of membrane shape, membrane size, heater/hot-film length and M e m b r a n e (size) to H e a t e r (hot-film length) Ratio (MHR) on sensors’ conductive heat losses. Therefore, in this paper we have provided experimental evidence of dependence of conductive heat losses in membrane based MEMS hot-film flow sensors on MHR by using eight MEMS hot-film flow sensors, fabricated in a 1 µm silicon-on-insulator (SOI) CMOS foundry, that are thermally isolated by square and circular membranes. Experimental results demonstrate that: (a) thermal resistance of both square and circular membrane hot-film sensors increases with increasing MHR, and (b) conduction losses in square membrane based hot-film flow sensors are lower than the sensors having circular membrane. The difference (or gain) in thermal resistance of square membrane hot-film flow sensors viz-a-viz the sensors on circular membrane, however, decreases with increasing MHR. At MHR = 2, this difference is 5.2%, which reduces to 3.0% and 2.6% at MHR = 3 and MHR = 4, respectively. The study establishes that for membrane based SOI CMOS MEMS hot-film sensors, the optimum MHR is 3.35 for square membranes and 3.30 for circular membranes, beyond which the gain in sensors’ thermal efficiency (thermal resistance) is not economical due to the associated sharp increase in the sensors’ (membrane) size, which makes sensors more expensive as well as fragile. This paper hence, provides a key guideline to MEMS researchers for designing the square and circular membranes-supported micro-machined thermal (hot-film) flow sensors that are thermally most-efficient, mechanically robust and economically viable.

scholarly journals The influence of heat loss from pipes in an unheated basement on the heating energy consumption of an entire typical apartment building

2020 ◽  
Vol 172 ◽  
pp. 12005
Author(s):  
Anti Hamburg ◽  
Targo Kalamees
Keyword(s):  
Energy Balance ◽  
Heat Loss ◽  
District Heating ◽  
Building Energy ◽  
Energy Performance ◽  
Heat Losses ◽  
Hot Water ◽  
Limited Information ◽  
Apartment Building ◽  
Heating Energy Consumption

The majority of old apartment buildings were designed with an unheated basement. Building service systems such as district heating heat exchangers and pipes for domestic hot water and for space heating are usually located in this unheated basement. In addition, these locations are connected with shafts. All these pipe’s heat losses increase air temperature in the basement. If these losses are included into the building energy balance, then they decrease heat loss through the basement ceiling. The basement’s heat balance is also dependent on heat loss from the basement envelope and outdoor air exchange in the basement. In early stages of design, designers and energy auditors need rough models to make decisions in limited information conditions. Once the effects of heat losses from pipes become apparent, they need to be factored into the buildings energy balance, and their effects on heat loss through the basement ceiling needs to be calculated. In this paper we analyse the effect these heat losses have on the service system’s heat gains and heat loss through an uninsulated basement ceiling at different basement insulation levels and with different thicknesses of pipe insulation. From our study we found that pipe losses in the basement increase the building energy performance value by at least 4 kWh/(m²∙a) and their impact on a renovated apartment building is very important.

scholarly journals A Fast Prediction Model for Heat Transfer of Hot-Wall Heat Exchanger Based on Analytical Solution

2018 ◽  
Vol 9 (1) ◽  
pp. 72 ◽  
Author(s):  
Wenju Hu ◽  
Peng Jia ◽  
Jinzhe Nie ◽  
Yan Gao ◽  
Qunli Zhang
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Thermal Resistance ◽  
Heat Conductivity ◽  
Convective Heat Transfer Coefficient ◽  
Side Wall ◽  
Analytic Solutions ◽  
Heat Convection ◽  
Thermal Engineering ◽  
Fast Prediction

The hot-wall heat exchanger (HWHE) has been widely used in thermal engineering fields such as ceiling radiant heating/cooling, refrigerator condenser, solar heat collection, and high-temperature heat recovery. However, the numerical simulation normally used for heat transfer prediction in HWHE is usually not as convenient as the analytic solutions in engineering applications. In this paper, a new heat transfer mathematical model of HWHE-based on analytic solutions was developed, which could be much faster to obtain the heat transfer properties of HWHE. The proposed model was validated under four conditions with literature values, which showed that the deviations of heat flux are 2.53%, 0.99%, 2.12%, and 1.96%, indicating its accuracy is satisfied. The model was then used to analyze the thermal property of HWHE. The results show the thermal resistance caused by panel with heat convection and conduction accounts for 96.54% of HWHE thermal resistance, and the thermal resistance caused by heat convection on the surface of panel is 74.43%. The analyzation results also show that adding aluminum foil around pipes could decrease HWHE thermal resistance by 5.11%. Besides, the influence of pipe diameters, pipe distance, pipe heat conductivity, side wall heat conductivity, and convective heat transfer coefficient on the heat transfer performance of HWHE was analyzed. The research in this paper can be used for fast prediction and optimization of heat transfer in HWHE.

Acoustic Resonance in a Reservoir-Double Pipe-Orifice System

2012 ◽  
Author(s):  
Arris S. Tijsseling ◽  
Qingzhi Hou ◽  
Bjørnar Svingen ◽  
Anton Bergant
Keyword(s):  
Wave Reflection ◽  
Large Diameter ◽  
Acoustic Resonance ◽  
Mode Shapes ◽  
Nonlinear Excitation ◽  
Pipe System ◽  
Fundamental Frequencies ◽  
Supply Pipe ◽  
Constant Head ◽  
Double Pipe

Acoustic resonance in a two-pipe system is simulated with four different models for the periodic excitation. Analytical solutions are provided in full for the three linear excitations. Exact numerical results are presented for the nonlinear excitation. The influence of a large-diameter supply pipe (instead of a constant-head reservoir) on the system’s fundamental frequencies and mode shapes is studied. The peculiar behaviour of wave reflection at an orifice is fully explained.

scholarly journals Investigating the Factors That Reduce the Urban Gas Pipeline Vulnerability to Explosion Threats

2019 ◽  
Author(s):  
Mohammad reza Fallah Ghanbari ◽  
Mohammad Eskandari ◽  
Ali Alidoosti
Keyword(s):  
Soft Soil ◽  
Shell Element ◽  
Friction Angle ◽  
Burial Depth ◽  
Gas Pipelines ◽  
Three Dimensional Model ◽  
Buried Pipelines ◽  
Burial Site ◽  
Pipe System ◽  
Abaqus Software

Introduction: Buried pipelines used to distribute water, gas, oil, and etc. are considered as one of the vital arteries. The experiences of the past wars have confirmed that the invading country focuses on bombing and destroying vital centers, and that gas pipelines can be a source of serious personal and financial losses as an important transmission arteries during war in the event of damage Methods: The vulnerability of buried urban gas pipelines to explosion was determined and the methods for reducing the vulnerability of pipelines were investigated. To this end, the three-dimensional model of the soil-pipe system in ABAQUS software was used to study the effect of factors affecting the pipe behavior, including pipe diameters, diameter to pipe thickness, internal friction angle of soil, soil type, amount of explosives, depth of buried, the distance of explosion site to the pipe burial site, has been investigated on the pipe deformation capacity according to the ALA regulation. The soil was modeled using Solid three elements and shell element. For parametric studies, analyses were performed by the finite element method using ABAQUS software 6.10.1. Results: Studies were conducted for 4 and 12 inch diameter, diameter/thickness ratio of 26, 21 and 35, burial depth of 1, 2, 3 and 4 meters, the explosive charge of 15, 30, 45, 60 and 200 kg TNT and for soil material, hard, soft and clay sands. The results showed that proper burial depth had the most effect in reducing the vulnerability of pipelines against explosive threats. By increasing the pipe thickness and increasing the diameter and applying soft soil around the pipe, a better behavior of the pipe was observed during the explosion Conclusion: To reduce the vulnerability of gas pipelines against explosive threats, the use of buried pipelines has a greater effect on reducing damage due to explosion compared to other parameters, and it is recommended to use this method to increase the resilience of highly important gas pipelines.

scholarly journals Analysis of a novel high performance induction air heater

2018 ◽  
Vol 22 (Suppl. 3) ◽  
pp. 843-853 ◽  
Author(s):  
Umit Unver ◽  
Ahmet Yuksel ◽  
Alper Kelesoglu ◽  
Fikret Yuksel ◽  
Halil Unver
Keyword(s):  
Flow Field ◽  
Cross Section ◽  
Flow Rate ◽  
Thermal Efficiency ◽  
High Performance ◽  
Control Volume ◽  
Thermal Power ◽  
Heat Losses ◽  
Flow Rates ◽  
Air Mass

This study represents an experimental and numerical investigation of the enhanced prototypes of the induction air heaters. For this purpose, flow field is enhanced in order to avoid turbulence. The air mass flow rate, outlet construction and the application of insulation of the outer surface of the heater were selected as the performance enhancing parameters. Depending on the exit construction, the new designed prototypes are named as K-2 and K-3. Experiments were performed under two groups for three various flow rates. In the first group, non-insulation situation is examined. In the second group tests, insulation is applied to the outside of windings and inlet-outlet flaps which constitute the boundary of the control volume for the prevention of heat losses. The increasing flow rate boosted the thermal efficiency by 9%. Each of insulation and enlarging exit cross section increased the thermal efficiency by 13%. It was observed that the thermal power transferred to air with the new prototypes increased about 246 W more than the previous designs. The thermal efficiencies of the K-2 and K-3 type heaters were calculated as 77.14% and 87.1%, respectively.

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