Heat Carrier Medium Research Articles

Increasing the Efficiency of Ecological Solar Panels Combined with the Building’s Roof

This article is devoted to increasing the efficiency of ecological solar panels with their combination with the house’s roof. A solar panel construction that combines both the solar collector and the building cover is considered. This work investigates the efficiency of solar panels depending on the type of coating, heat-carrying medium mass flow rate, tube diameter, and the distance between the tubes. Among the coatings, Grafplast PDA roofing material is the most effective. Prandelli/Tuborama tubes with a diameter of 16 mm are recommended. The diameter of the tubes significantly affects the efficiency of the solar panel only at low intensity of solar radiation.

Study on thermal properties of bio-char prepared by photo-thermal pyrolysis

Photo-thermal pyrolysis provides a new method for the preparation of bio-char through the energy absorption of the intermittent solar energy into the carbon materials to achieve the energy storage and negative carbon emissions. The evolution of thermal properties of different chars prepared by photo-thermal pyrolysis with different final-reaction temperatures and heating rates was studied. The study of specific heat capacity showed that the final-reaction temperature had a stronger impact than the heating rate. At a final-reaction temperature of 800 °C, the maximum specific heat capacity of rice straw and pine char reached 1595 J·kg−1·K−1 and 2070 J·kg−1·K−1 respectively. Measurements of thermal conductivity showed that the higher final-reaction temperature and the higher heating rate both increased the thermal conductivity of char. Rice straw char had a maximum value of 0.2203 W·m−1·K−1 at 800 °C and 500 °C/min, which was almost twice the thermal conductivity of char at 400 °C and 50 °C/min. Further correlation analysis showed the physical structure of the char, especially its density and pore size, had a greater impact on thermal conductivity. The multiple linear model of thermal conductivity was established, which not only had a good fitting effect but also well predicted the thermal conductivity of another kind of char, and the error was within 10%. This study demonstrates the potential of photo-thermal pyrolysis char as a heat carrier and light absorption medium during photo-thermal pyrolysis.

Influence of spinning flower structure inserts in the thermal performance of LS-2 model of parabolic trough collector with ternary hybrid nanofluid

Parabolic solar trough collector is the most widely accepted technology to use inexhaustible energy. Present research work proposed LS-2 model of parabolic trough collector with various spinning flower inserts and three particles based nanofluid as a heat-carrying medium. Main intention of this examination is to lower the temperature gradient in fluid flow and provide uniform distribution of heat flux on the receiver's outermost surface. A total of ten cases of PTC are examined in ANSYS 22 Fluent. Nine steady receivers are equipped with spinning flower inserts and one without inserts. Hybrid nanofluids with 1% vol. content are attained by blending aluminum oxide, copper oxide, and graphene oxide with water as base fluid. This evolution focuses on the consideration of spinning inserts in the receiver with a range of speed from 0 to 15 rad/s. The flow rate is from 0.016 kg/s - 0.033 kg/s respectively. Highest enhancement for thermal efficiency and heat transfer coefficient are 30.87% and 98.34% for case-9 at 15 rad/s inserts speed than receiver without inserts using nanofluid-6 at 0.033 kg/s. Under the same condition, the highest increment for the pump work requirement is 21.29% for case-9 than receiver without inserts. This means increment of pump work is insignificant than thermal performance improvements.

Numerical study on heat storage efficiency of broken rock mass under different CO2 injection conditions

The application of energy storage technology can solve the problems of randomness and volatility in the development and use of renewable energy, such as wind and solar energy, and effectively improve energy utilization. Rock heat storage is one of the primary forms of sensible heat storage. The heat storage efficiency and heat storage capacity of rock packed bed are important indicators to measure the energy storage effect of a rock energy storage system. This paper takes CO2 as the heat-carrying medium and broken granite grains as the packed bed matrix of the energy storage system. It establishes a porous medium thermal-hydraulic-mechanical coupling model of the broken rock bed. The heat injection and production process of the large-sized rock bed heat storage system is simulated using the COMSOL finite element software, and the heat storage efficiency and heat storage capacity of the broken rock bed is analyzed under different fluid injection pressures and injection temperatures. The results show that: 1) With the increase of CO2 injection pressure, the heat storage and heat production speed of the heat storage system will increase, and the heat storage rate changes from two stages of “low rise - slow decline” to four stages of “rapid increase—stability—rapid decrease—stability”; 2) With the increase of CO2 injection temperature, the maximum heat storage capacity of the rock bed heat storage system will increase. Due to the increase in the temperature gradient between CO2 and the rock bed, the heat storage and the heat production time of the heat storage system will increase, and its speed will decrease.

A novel photovoltaic/thermal (PV/T) solar collector based on a multi-functional nano-encapsulated phase-change material (nano-ePCM) dispersion

Overheating is a major problem encountered by photovoltaic (PV) cells that significantly deteriorates their performance and shortens their lifetime. For the first time, this study numerically investigated employing a nano-encapsulated phase-change material (nano-ePCM) dispersion in a double-pass photovoltaic/thermal (PV/T) solar collector, where the multi-functional nano-ePCM dispersion simultaneously operates as an optical filter, heat carrier, and storage medium. The water-dispersed nano-ePCM particles were made of silica shells and paraffin-based cores. The proposed system was optically, thermally, and electrically modeled and evaluated after rigorous validation against published results. The performance of the PV/T system was analyzed upon varying the PCM core material, flowrate, solar intensity, particle size and loading, and channel depth and length. In addition, the proposed system (SYS-1) was compared to two alternative configurations, where one was based on a cooling channel below the PV cells without an optical filtration channel (SYS-2), and the other was based on an optical filtration channel above the PV cells without a cooling channel (SYS-3). To investigate the optical filtration capabilities of the nano-ePCM dispersion, a performance metric known as the ‘spectral match’ (SM) was proposed. Results showed that all ePCM dispersions exhibited a SM > 70 % when the PCM cores were in their liquid phase and a SM > 30 % while in solid phase. As compared to SYS-2 and SYS-3, at the lowest investigated flowrate (0.0026 kg s−1), the proposed PV/T system exhibited mean cell temperatures lower by 5 and 10°while offering relative thermal exergy enhancements of 66 and 208 %, respectively. This was attributed to allowing the PV cells to operate at temperatures substantially lower than the dispersion outlet temperature to achieve both high-grade thermal outputs and enhanced PV efficiencies. This study paves the way for novel PV/T collectors that employ smart, multi-functional fluids offering superior electrical and thermal performance.

Analysis of a direct vapor generation system using cascade steam-organic Rankine cycle and two-tank oil storage

A direct vapor generation solar power system using cascade steam-organic Rankine cycle and two-stage oil tanks is proposed. It offers a significantly enlarged storage capacity due to the unique discharge operation mode. Synthetic oil Therminol® VP-1 is used as the heat carrier and storage medium. Compared with the direct steam generation system, the steam turbine inlet temperature is elevated from 270 °C to 311 °C. Thermodynamic analysis indicates that the optimal equivalent heat-to-power conversion efficiency (ηeq,opt) is 27.91% when benzene is used as the bottom fluid and the mass of oil is 1000 tonnes. ηeq,opt is raised by 7.72–11.60% for the selected four organic fluids as compared with the direct steam generation type. The temperature drop of oil during discharge can reach about 280 °C. Economic studies demonstrate that the proposed system is more cost-effective. Its equivalent payback period is less than 5 years for a 10 MW system with 2000 tonnes of oil. Further investigation shows that it is also more advantageous than a conventional thermal oil-based indirect solar power system due to the cost reduction in heat storage.

Numerical Simulation on Heat Recovery Efficiency of Different Working Fluids in High-Temperature Rock Mass

It is of great significance for the sustainable development of global energy to develop hot dry rock (HDR) geothermal resources by using enhanced geothermal system (EGS) technology. Different working fluids in EGS have different heat recovery efficiencies. Therefore, this paper takes water and CO2 as the heat-carrying media and establishes a thermal hydraulic mechanical coupling model to simulate the heat recovery process in high-temperature rock mass. By considering the different confining pressures, rock temperature, and injection pressure, the advantages of H2O-EGS and CO2-EGS are obtained. The results show that with the increase of confining pressure, the heat recovery efficiency of water is significantly higher than that of CO2, but at higher reservoir temperature, CO2 has more advantages as a heat-carrying medium. The net heat extraction rate will increase with the increase of injection pressure, which indicates that the mass flow rate plays a leading role in the heat recovery process and increases the injection pressure of fluid which is more conducive to the thermal recovery of EGS. This study will provide a technical guidance for thermal energy exploitation of hot dry rock under different geological conditions.

An experimental investigation on a novel direct-fired porous boiler for the low-pressure steam applications

Heat is the most essential form of energy for mankind lives. Steam is the most widely used as heat-carrying medium in the world. The boiler is the best system for the conversion of chemical energy contained in fuels into steam or hot fluid. According to the efficiency of all existing boilers, one of the most important factors that substantially affect this boiler performance index is the stack losses. This research proposed a novel direct-fired porous boiler (DPB). Because of it has no stack losses, this proposed boiler could outperforms all of the existing boilers. The purpose of this article is to discuss the potential of enhancing the suggested DPB performance by using different physical characteristics of packed-bed porous medium (PPM). The experimental results show that among the four most bed shapes available in the market and have a high heat transfer aspect, the hex-nut shape has been selected to use in the proposed DPB. At the heat input rate of about 14 kW, the steam generation rate of about 20 kg/h, (at 1.5 barg and 300 °C), is obtained. Because it has only surface heat loss, thermal efficiency of more than 98% can be achieved. It can be concluded that the possibility of using a hex-nut bed as a packed bed porous medium in a low-pressure porous boiler is confirmed with the proposed boiler.

Energy Balance of a Low Energy House with Building Structures with Active Heat Transfer Control

A qualitatively new dimension has been introduced to the issue of building structures for energy-efficient buildings by the system of Active Thermal Insulation (ATI), which is already applied in the construction of such buildings. ATI are embedded pipe systems in the envelope structures of buildings, into which we supply a heat-carrying medium with adjusted temperature, so this constitutes a combined building-energy system. This introduces the concept of an internal energy source understood as an energy system integrated into the zone between the static part and the thermal insulation part of the building structure envelope. Under certain conditions, the ATI can serve as a heat recuperator or as an energy collector for a heat pump application. ATI consists of pipe systems embedded in building structures, in which the medium circulates heated by energy from any heat source. The function of the system is to reduce or eliminate heat losses through non-transparent structures in the winter and at the same time to reduce or eliminate heat gains in the summer. It is especially recommended to apply heat sources using renewable energy sources due to the required low temperatures of the heating medium and thus shorten the heating period in the building. Also recommended is to apply ATI for the use of waste heat. Buildings with a given system show low energy consumption and therefore meet the requirements of Directive no. 2018/844/EU, according to which, from 01.01.2021, all new buildings for housing and civic amenities should have energy needs close to zero.

Combustion Simulation of 130KW Large Cylinder Natural Gas Heater with Intermediate Heat Carrier Medium

In order to study the combustion temperature distribution of the fire tube and flue tube of the large cylinder natural gas heater with intermediate heat carrier medium, and to select a more appropriate combustion method, this paper separately simulates two kinds of combustion methods: premixed combustion and diffusion combustion. Using a standard turbulence model to describe the turbulent conditions of the flue gas, the turbulent diffusion combustion model and the vortex crushing model were used to simulate the diffusion combustion and the premixed combustion respectively. The results show that this structural model is more suitable for the diffusion combustion method.

Studi Sistem Injeksi Inhibitor Korosi terhadap Kandungan Orthofosfat dan Seng sebagai Parameter Kendali Korosi pada Sistem Pendingin Sekunder Rsg-gas

Reaktor Serba Guna G.A Siwabessy (RSG-GAS) was built since 1983. RSG-GAS is a type of research reactor equipped with heat carrier and cooling system which serves to remove heat arising from fission reactions. In the heat carrier medium, the reactor equipped with a secondary cooling system using water originating from PAM Puspiptek. Water used in secondary cooling systems can cause some major problems of crust, corrosion, and moss or microorganisms. In this research, the phosphorus (orthophosphate), zinc, and conductivity and pH in the secondary cooling system have been measured to determine whether or not the flow rate of the injection system is used. Determination of concentration of the elements was performed using a DR / 2400 spectrophotometer portable device with ZincoVer 5 Powder Pillow reagent, cyclohexane for zinc concentration, and PhosVer 3 phophate for phosphorus concentration. From the results obtained, the overall flow rate of injector injection of 1.7 L / h gives a good result. Significant differences occurred only in conductivity values ​​dated July 21, 2009 both in piped water and cooling towers exceeding 950 μs / cm. And the value of orthophosphate concentration dated August 4, 2009 that exceeds 10 ppm.

An Analysis of the Influence of Protective Films on the Inner Surfaces of CCPP Headers and Steam Pipelines on Their Thermal Stress State

At present, the main attention of researchers is paid to the deterioration of heat transfer when heating the outer surface of the pipe with the liquid or steam, flowing inside it, in the presence of films or deposits on its inner surface. However, when pipe is heating by heat carrier medium, flowing inside it, film on the inner pipe surface serve a dual protective function, protecting the pipe from corrosion and reducing its thermal stress. The article represents the results of the computational analysis of protective films influence on the thermal stressed state of headers and steam pipelines of combined-cycle power plants (CCPP) heat-recovery steam generators at different transient operating conditions particularly at startups from different initial temperature states and thermal shock. It is shown that protective films have a significant influence on the stresses magnitude and damage accumulation mainly for great temperature disturbances (for thermal shock). Calculations were carried out at various thicknesses of films and assuming that their thermal conductivity less than thermal conductivity of the steam pipelines metal.

Novel multi-tubular fixed-bed reactors’ shell structural analysis based on numerical simulation method

In the present contribution, a numerical study of fluid flow and heat transfer performance in a pilot-scale multi-tubular fixed-bed reactor with a novel configuration for propylene-to-acrolein oxidation reaction is presented using a three-dimensional computational fluid dynamics method (CFD) to ensure the uniformity condition using molten salt as a heat carrier medium on shell side. The effects of multiscale structural parameters including the number of baffles, baffles cut, central nontube region and the number of flow channels on pressure drop and heat transfer are considered. The simulations suggest that heat transfer coefficient per pressure drop is reduced with increasing number of baffles. By the single factor sensitivity analysis it was shown that the central region is the key factor in the structural design of a multi-tubular fixed-bed reactor.

Multicriterial optimization of the energy efficiency of the thermal preparation of raw materials

Issues related to the thermal treatment of raw materials in conveyor calcination machines are addressed. The main operating part in this type of apparatus is a moving thick layer of disperse raw material with the crosswise delivery of a heat-carrier medium. Thermally activated technological processes are carried out in disperse raw material layer, such as drying, calcination (decarbonization), and sintering. The technological conditions and completeness of processing determine the quality of the final product. In order to create highly effective resource- and energy-saving technologies for the rational use of raw materials, fuel, and power sources, the results that make it possible to control the technological processes in a thick layer of disperse raw materials are obtained based on the mathematical model and using the methods of multicriterial optimization.

Numerical investigation of flow and heat transfer in a novel configuration multi-tubular fixed bed reactor for propylene to acrolein process

In the present contribution, a numerical study of fluid flow and heat transfer performance in a pilot-scale multi-tubular fixed bed reactor for propylene to acrolein oxidation reaction is presented using computational fluid dynamics (CFD) method. Firstly, a two-dimensional CFD model is developed to simulate flow behaviors, catalytic oxidation reaction, heat and mass transfer adopting porous medium model on tube side to achieve the temperature distribution and investigate the effect of operation parameters on hot spot temperature. Secondly, based on the conclusions of tube-side, a novel configuration multi-tubular fixed-bed reactor comprising 790 tubes design with disk-and-doughnut baffles is proposed by comparing with segmental baffles reactor and their performance of fluid flow and heat transfer is analyzed to ensure the uniformity condition using molten salt as heat carrier medium on shell-side by three-dimensional CFD method. The results reveal that comprehensive performance of the reactor with disk-and-doughnut baffles is better than that of with segmental baffles. Finally, the effects of operating conditions to control the hot spots are investigated. The results show that the flow velocity range about 0.65 m/s is applicable and the co-current cooling system flow direction is better than counter-current flow to control the hottest temperature.

Fluidized Bed Technology for Concentrating Solar Power With Thermal Energy Storage

A generalized modeling method is introduced and used to evaluate thermal energy storage (TES) performance. The method describes TES performance metrics in terms of three efficiencies: first-law efficiency, second-law efficiency, and storage effectiveness. By capturing all efficiencies in a systematic way, various TES technologies can be compared on an equal footing before more detailed simulations of the components and concentrating solar power (CSP) system are performed. The generalized performance metrics are applied to the particle-TES concept in a novel CSP thermal system design. The CSP thermal system has an integrated particle receiver and fluidized-bed heat exchanger, which uses gas/solid two-phase flow as the heat-transfer fluid, and solid particles as the heat carrier and storage medium. The TES method can potentially achieve high temperatures (>800 °C) and high thermal efficiency economically.

Research of Gas Heater with Different Intermediate Heat Carrier Medium

The gas heater, reliable as it is, is nevertheless slow in getting started, and is one of the low-efficiency energy consumption equipments adopting the indirect heating by the intermediate heat carrier medium. Apparently, the form of heat transfer process of the intermediate heat carrier medium, i.e. the flow field organization in the large capacity cylinder, is one of the key elements that can improve the thermal efficiency of gas heater. Experimental investigation and analysis of the flow condition and temperature distribution between the water and ethylene glycol in the cylinder were carried out. Based on the investigations on medium selection and heater’s integral structure and combining with the engineering practical needs, effective measures to improve the efficiency of gas heaters have been brought forward in this article and the technology has got itself the China patents.

Simulation of steel cooling in crystallization tanks

The results of a steel cooling simulation in the process of obtaining hollow billets using a finned heat pipe as the core model after heating by an electric heating element are presented. The novelty is confirmed by patents for techniques of obtaining hollow billets and crystallization tank cooling using a heat pipe. Heat power values passed within a heat pipe model and high-temperature pipe in the process of steel cooling are found, and a heat-carrying medium mass in high-temperature pipe and its sizes are determined, along with the cast steel temperature and parameters of the heat-carrying media.

Correspondence between heat-transfer coefficients in steady and unsteady processes

An experimental study is made of the unsteady flow of heat through an element of a heat-exchanger wall for various flow conditions of the heat-carrying medium. These processes are compared with the processes occurring in the simple heating of the element (i.e., with one end thermally insulated to prevent through-flow of heat). The comparison is made for the same flow conditions of the heat-carrying medium. The conclusions of the thought experiment described in [1] are confirmed.