Thermal Insulation Systems Research Articles

Comparative Study on Thermodynamic Characteristics of Composite Thermal Insulation Systems With Liquid Methane, Oxygen, and Hydrogen

Abstract Composite passive insulation technology has been proved to be an effective method to reduce heat leakage into the cryogenic storage tank. However, the current related research mainly focused on liquid hydrogen (LH2). The thermophysical properties of different cryogenic liquids and the thermal insulation materials at different temperatures are significantly different, so whether the results related to LH2 are applicable to other cryogenic liquids remains to be further determined. In fact, the insulation technology of LH2 itself also needs further study. In this paper, a thermodynamic calculation model of a composite insulation system including hollow glass microspheres (HGMs), multilayer insulation (MLI), and self-evaporating vapor cold shield (VCS) has been established. The accuracy of the calculation model was verified by the experimental results, and a comparative study on thermodynamic characteristics of the composite thermal insulation system with liquid methane, liquid oxygen (LO2), and LH2 was carried out. The results show that the heat leakage reduction of the proposed system for liquid methane, LO2, and LH2 is 25.6%, 29.7%, and 64.9%, respectively, compared with the traditional SOFI + MLI system (1 × 10−3 Pa). The type of liquid and the insulation system structure has a relatively large influence on the VCS optimal position. While for a specific insulation system structure, the insulation material thickness, storage pressure, and hot boundary temperature have a weak influence on the VCS optimal position.

Hermetically sealed porous-wall hollow microspheres enabled by monolithic glass coatings: Potential for thermal insulation applications

Thermal insulation materials are crucial to improve the energy performance of buildings and industrial applications. We report an approach to create hermetically vacuum-sealed silica-based hollow microspheres that can lower the thermal conductivity of closed-cell insulation materials. The wall structure of these hollow microspheres includes a reticulated network of pores or channels that extend through the thickness of the wall. When a thin layer of glass material is applied to the wall exterior, followed by a vacuum-assisted thermal treatment process, the coated microsphere surfaces display a highly dense conformal coverage and near-complete elimination of surface porosity. The sealing efficiency of these microspheres is verified by trapping argon within their cavities as well as through evacuating their hollow cores. Notably, incorporating the evacuated microspheres into a polymer matrix resulted in ∼27% enhancement in its thermal insulation performance and no notable loss of performance was observed following three months of exposure to ambient conditions. Thus, we believe that the present study offers a commercially viable strategy that opens the door to applications of such inorganic hollow particles in areas ranging from vacuum-based thermal insulation systems to catalysis, separation technologies, and medical fields.

Predicting the conductive heat transfer through evacuated perlite based vacuum insulation panels

The core material contributes ≥40% of the total cost of a fumed silica based vacuum insulation panel (VIP). Expanded perlites, which come at approximately one-tenth of the current price of fumed silica, have been identified as potential core material candidates. Though, the characteristic vacuum insulation properties i.e. evacuated thermal conductivity and half pressure value of expanded perlites are not suitable for most applications, these can be improved by altering their structural properties like particle size, pore size, porosity etc. during manufacture. The knowledge of the relationship between structural properties and the thermal conductivity of perlite is key to develop improved thermal performance VIPs.In the present work, it has been found that the thermal conductivity of the perlite cores lies between the thermal conductivities of two regular packing orders – simple cubic packing and the hexagonal close packing. Owing to the complex geometries involved, the thermal conductivity of particle beds arranged in these two packing structures was numerically calculated using finite element method. The dependence of the thermal conductivity on five parameters (particle size, intra-particle pore size, porosity, internal gas pressure and contact ratio) was observed and correlated with existing studies in literature. The model was also validated by experiments performed on expanded perlite. The developed framework can be employed to produce bespoke perlites for most cost-effective thermal insulation systems.

Multipurpose Retrofitting of a Tower Building in Brescia

The paper aims to report a proper low-impact integrated study approach for the energy and seismic retrofitting of a tower building located in the city centre of Brescia (Italy). The building consists of a group of aggregate buildings built in the 1950s, from which emerged an 11-storey tower. It was built with the technology of the time by means of a perimeter and spine framed structure in reinforced concrete, double perimeter infill with a hollow brick air chamber, external cladding on the main fronts with small Botticino marble tiles. The building is registered by the Ministry of Cultural Heritage for its facade and is located in a seismic zone of category two. When work began, the construction was in a class three; thus, the whole project was updated to obtain the new seismic authorisation. The coating showed progressive decay, with dangerous structural instability of the heavy coating. The design team decided to adopt wider corrective action compared to the observed phenomenon, integrating it with a local seismic and global energy improvement through the insertion of a ventilated wall in the building and the realisation of accurate thermal and energy insulation systems. At the end of the intervention, this building became the first condominium in Italy in 2018, certified in class A and upgraded with sustainability criteria in which the application of the GBC Italy (Green Building Council) Condominiums protocol, currently in its final publication phase for the energy–environmental sustainability of condominiums, has been tested.

RESEARCH OF THE INFLUENCE OF EXTERNAL VERTICAL ENVIRONMENTAL STRUCTURES ON THE SPREAD OF FIRE ON THE SURFACE OF WALLS

Purpose. Using FDS modelling to investigate the influence of external vertical enclosing structures on the spread of fire on the surface of external wall structures with facade insulation with combustible insulation.Methods. Using the software package Pyrosim performed тumerical modelling of the dynamics of development and spread of fire on the surface of the thermal insulation and finishing system, which serves as a user shell for the program Fire Dynamics Simulator (FDS). To visualize the results of calculations, the software module of the PyroSim Smoke view system was used, which allows building appropriate graphical representations of temperature distributions. This system also allows you to monitor the dynamics of temperature fields and reproduce the heating process with animation.Results. With the help of computer modelling of fire test parameters of facade insulation system for fire propagation in FDS environment, numerical and graphical indicators were obtained by computer simulation of the fire test parameters of the facade insulation system for fire propagation in the FDS environment. They characterize the process of occurrence, spread and development of fire by the surface of the facade insulation system. Also, we established the influence of external vertical enclosing designs on a fire surface of outside walls with a warming of a facade by a combustible heater. The obtained results of numerical modelling of the parameters of the fire test of the facade insulation system for the propagation of fire in the FDS environment indicate that the overall standard deviation in the theoretical data was higher than the results of experimental stud-ies. Thus, the presence in the structure of a fragment of the building vertical wall (inner corners of the building) creates a “shielding effect”, i.e. the flame emanating from the window is reflected and the temperature on the surface of external walls with facade insulation rises significantly. Thus, for thermocouples T15-T17 the temperature rises by 140-220 °C; for thermo-couples T19-T21 – by 180-350 °C; for thermocouples T27-T29 – by 110-190 °C, respectively.In addition, the presence of external vertical enclosing structures on the facade of the building contributes to the increase in temperature and inside the structures of external walls with facade insulation, as evidenced by the readings of thermocouples T33 and T35 – an increase of 50-100 °C; thermocouples T36 and T38 – increase by 50-180 °C.Practical value. The results of numerical simulations obtained by the author are aimed at the use of design organizations in the installation of fire belts using noncombustible mineral wool boards in the inner corners of the building as insulation in the presence of window and balcony openings to prevent fire from spreading on facade systems in residential buildings.

Thermal Performance of Double-Pane Lightweight Steel Framed Walls with and without a Reflective Foil

One strategy to increase energy efficiency of buildings could be the reduction of undesirable heat losses by mitigating the heat transfer mechanisms across the building envelope. The use of thermal insulation is the simplest and most straightforward way to promote thermal resistance of building elements by reducing the heat transfer by conduction. However, whenever there is an air cavity, radiation heat transfer could be also very relevant. The use of thermal reflective insulation materials inside the air gaps of building elements is likewise an effective way to increase thermal resistance without increasing weight and wall thickness. Some additional advantages are its low-cost and easy installation. In this work, the performance of a thermal reflective insulation system, constituted by an aluminium foil placed inside an air cavity between a double pane lightweight steel framed (LSF) partition, is experimentally evaluated for different air gap thicknesses, ranging from 0 mm up to 50 mm, with a step increment of 10 mm. We found a maximum thermal resistance improvement of the double pane LSF walls due to the reflective foil of around +0.529 m2∙°C/W (+21%). The measurements of the R-values were compared with predictions provided by simplified models (CEN and NFRC 100). Both models were able to predict with reasonable accuracy (around ±5%) the thermal behaviour of the air cavities within the evaluated double pane LSF walls.

Numerical simulation on double diffusion natural convection of a power-law nanofluid within double wavy cavity

In the present paper, the effect of double diffusion natural convection fluid flow inside the double wavy enclosure using the mesh-free method is investigated. The enclosure is filled with nanofluid whose base fluid is non-Newtonian. The results are obtained for the variation in Brownian motion parameter (0.2–0.8), buoyancy ratio parameter (0.2–1), power-law index (0.2–1), thermophoresis parameter (0.2–0.8), Rayleigh number (103–105), and Lewis number (1–5) on mass and heat transfer. It is explored that the mass and heat transfer rate increases with increase in the Rayleigh number and buoyancy ratio. Heat transfer rate decreases with increase in the thermophoresis parameter, Lewis number, Brownian motion, and power-law index, whereas mass transfer rate increases. Such type of enclosure has direct application in heat exchanger devices, the double-wall thermal insulation system, and microelectronic devices. Parallel implementation with the hybrid [EFGM (element free Galerkin method)/FEM (finite element method)] method has been used for the reduction of the running cost to ensure efficiency, which is the novel contribution of the author.

Research of Heat Losses of Solar Collectors and Heat Accumulators

The article discusses the features of heat losses by convection and radiation of flat solar collectors on the basis of a non-stationary thermal model and program. The connection of heat losses with the generalized heat loss coefficient of solar collectors is shown. The article also deals with the problem of determining the distribution of temperatures and heat losses by convection and radiation of a thermal insulation system – accumulating body (water) for a spherical heat accumulator under symmetric boundary conditions. The problem is solved numerically according to the program developed on the basis of the proposed “gap method.” The method and program for the numerical calculation of heat losses and temperatures in time in a spherical two-layer heat accumulator with symmetric boundary conditions, taking into account both incident and intrinsic radiation, have been developed. The program has been developed for a “long” two-layer cylindrical heat accumulator of solar collectors.

Assessment of the Annual Transmission Heat Loss Reduction of a Refurbished Existing Building with an Advanced Solar Selective Thermal Insulation System

A numerical parameter sensitivity analysis of the design parameters of the recently published solar selective thermal insulation system (SATIS) has been carried out to enhance its thermal and optical properties. It turned out that the insulation properties of SATIS can be effectively improved by reducing the length of the glass closure element. Increasing the area share of the light conducting elements (LCEs) and decreasing their length-to-diameter (L/D) ratio were identified as key parameters in order to increase the solar gain. Two SATIS variants were compared with the same wall insulation without SATIS in a yearly energetic performance assessment. The SATIS variant with 10 mm length of the closure element, 44.2% area share of LCE, as well as front and rear diameters of 12 mm/9 mm shows an 11.8% lower transmission heat loss over the heating period than the wall insulation without SATIS. A new methodology was developed to enable the implementation of the computed solar gains of SATIS in 1D simulation tools. The result is a radiant heat flow map for integration as a heat source in 1D simulation models. A comparison between the 1D and 3D models of the inside wall heat fluxes showed an integral yearly agreement of 98%.

Preparation and properties of nanopore-rich cement-based porous materials based on colloidal silica sol

Cement-based porous materials (CPMs) with different dry densities were successfully prepared by using silica sol as pore-forming agent. The rheological behavior of the fresh CPMs was discussed, then pore structure, pore-forming mechanism of silica sol, dry density, compressive strength and thermal conductivity of CPMs were investigated and presented. The results indicate that nanopores in cement paste were formed in-situ by adding silica sol, which led to the optimization of pore structure of CPMs, thereby improving the properties of CPMs. When the substitution of cement matrix by silica sol reached to 95 vol%, CPM with a nanopore volume of 0.675 cc/g, dry density of 488 kg/m3, thermal conductivity of 0.081 W/(m·K) and compressive strength of 0.5 MPa was successfully obtained, showing excellent insulation performance. CPMs with achieved strengths and low thermal conductivities show great potential in the application of semi-structural and structural thermal insulation systems of buildings.

A Study of The Properties of Forming Mixtures Containing Polystyrene Wastes

Expanded polystyrene is widely used as a material for packaging, in modern construction as a heat and sound insulation layer, in thermal insulation systems for buildings, as well as tanks and pipelines. It is additionally used in foundry engineering for the production of models which are gasified during the production of castings from ferrous and non-ferrous alloys under the contact with liquid metal. The use of expanded polystyrene products is associated with waste generation, both in production and in consumption. About 40–50 kg/person of polystyrene waste is generated per year. The peculiarity of polymeric wastes is their resistance to aggressive environments. They do not rot and the destruction processes in natural conditions proceed rather slowly, with the formation of harmful substances that poison the environment. Therefore, the problem of the processing of waste from polymeric materials is of great importance, not only from the standpoint of environmental protection, but also due to the fact that in conditions of a shortage of polymer raw materials, this waste becomes a powerful raw material resource. This article describes the prospects for recycling expanded polystyrene wastes in foundry engineering. In this work, the properties of molding and core sands containing a combined binder, consisting of a solution of expanded polystyrene wastes in turpentine and clay were investigated, and their main characteristics (weight during stretching and crumbling) were determined. Molding and core mixtures, which contain only a binder in the form of a solution of expanded polystyrene in turpentine, have a crude strength of not more than 0.01 MPa. The introduction of a mixture of clay in the amount of 2–3% allows a crude strength of the mixture of up to 0.05 MPa to be obtained. After drying, the investigated mixtures containing a solution of expanded polystyrene wastes and clay have a tensile strength of up to 2.1 MPa. Mixtures into which a solution of polystyrene wastes and clay was introduced have an insignificant gas capacity and satisfactory gas permeability.

Analysis of the Structure of Heat Losses from Buildings and Benefits of Thermal Insulation Systems

The sources of energy are finite and are often found in unstable regions of the world, and we cannot assume at present that heat will be cheaper. Hence, and not only for these reasons, the issues of heat losses from buildings must be addressed. The paper investigates the issues of heat losses from buildings and analyses the benefits of thermal insulation of buildings. The thermal insulation of a building reduces the leakage of heat during the heating season and brings about savings in heat consumption amounting to tens of percent. In addition, when a building is insulated, the heating season may start later and end earlier. Typical thermal insulation technical modifications include the insulation of external walls, replacement of windows, roof insulation, insulation of the ceiling under the attic and above the cellar. Reducing the leakage of heat will reduce its consumption in heating and thus also cuts down air pollution with emissions produced by heating. The benefits of thermal insulation are in the economic, as well as technical sphere of building operation. The study compares the structure of heat losses and heat gains of apartment buildings from the 1970s, both in the insulated and uninsulated version, with houses complying with the current required standards and houses complying with the current recommended standards.

Influence of Thermal Alternation on the Interface between Insulation Layer and Bonding Mortar

The safety of the external thermal insulation system has been widely concerned by people. In this paper, strain gauges and temperature sensor are preset at the interface of bonding layer/insulation layer, bonding layer/mortar layer. The interface stress variation rules of graphite polystyrene board, polystyrene board and homogeneous board were studied under 30 times of thermal alternating environment and the test results were analyzed in combination with physical properties of the materials. The results show that the strain at the interface of the samples composed of three kinds of thermal insulation materials increases with the increase of the number of thermal alternating cycles. The total interfacial strain of the sample composed of homogeneous board is the largest, and that of graphite polystyrene board is the smallest.

Economic and Energy Analysis of Building Retrofitting Using Internal Insulations

The energy-saving requirements for most buildings focus on improving the insulation and airtightness of a building’s envelope. In this paper, the authors have investigated the effect of additional internal insulation on energy consumption for heating and cooling in a residential building. Energy performance analyses were conducted for buildings with four internal thermal insulation systems in three locations using the WUFI Plus software. The Global Cost Method and Simply Pay Back Time have been used to assess and compare the economic viability of the retrofit systems. The results show that, in relation to energy, retrofitting with internal wall insulation can be an alternative to traditional external insulation. The assessment of internal insulation for low-energy buildings, however, cannot be conducted based on economic criteria. The usual approach of Simply Pay Back Time has exceptionally long payback time, which is unacceptable. In turn, the Global Cost Method, can only be used to compare the applied materials. With high investment costs, thermo-modernization improvements do not contribute to significant savings. The conditions of thermal comfort and the analysis of temperature and steam pressure play a decisive role in assessing this type of solution.

Energy Optimization and Environmental Impact of an Office Building at Biskra City, Algeria: Life Cycle Assessment, Applied to the Building Envelope in Hot and Dry Climate

This work assesses the environmental impact generated by an office building in arid region throughout its life cycle (cradle to grave), by means of a Life Cycle Assessment (LCA). This study focuses on a comparison of different external wall systems that are conventionally used in building. With recycled materials and thermal insulation system, it’s possible to reduce demand of energy consumption, evaluate their environmental indicators impacts, and also reduce them, throughout the building life cycle. In doing so, this work can contribute not only to control energy, long-term economic growth, but also to address pressing social issues, and mainly environmental impacts. We use an environmental analysis with a thermal dynamic simulation, to test the hypothesis on a data base of hot and dry climate of Biskra city. The last part consists of a technical approach, indicating the economy is the use of ecological and recycled materials. The results of this study show that the exterior insulation system, obtained the best environmental scores, being 30% less than the interior insulation system and 50% less than the distributed insulation system. Also, recycled materials save energy in their manufacture, and building energy consumption for its use and have a reduced building impact on the environment throughout its life cycle (cradle to grave). This work shows how LCA application is not only feasible, but recommended because it is a decision support tool in the search for sustainability and make use of recycled materials.

Research on Seismic Test and Calculation Model for Improving Factor of Composite Board with Heat Preservation Function

Since the composition and stress state of thermal-insulation composite plates are extremely complex, it is difficult to conduct calculation using conventional methods. Further calculation on its composition structure is even more difficult. To settle this difficulty, this paper conducted experimental investigations on thermal-insulation composite plate and conventional composite plates, and a simplified calculation method with improved factors was deduced based on the experimental results. In this study, the influence of nonstructural thermal insulation system on the composite plate was specially considered. The calculated expressions are deduced, while the stiffness and damping (properties) are determined. Case analysis was carried out to validate the reliability and accuracy of the simplified calculation method of improvement factor. The research results indicate that the modeling difficulty and computational effort are greatly reduced, with relatively small errors. Hence, it is beneficial to the calculation and analysis of composite plates and global structures.

Experimental and Numerical Study on the Heat Transfer Characteristics of a Newly-Developed Solar Active Thermal Insulation System

A newly-developed solar active thermal insulation system (SATIS) is introduced with the main objective to accomplish a highly-dependent total solar transmittance on the irradiation angle. SATIS is also designed to obtain the maximum transmittance at a prescribed design irradiation angle and to reduce it remarkably at higher irradiation angles. A purely mineral thermal insulation plaster with micro hollow glass spheres is applied to manufacture the investigated SATIS prototype. Light-conducting elements (LCEs) have been introduced into SATIS and suitable closing elements have been applied. The SATIS prototype has been investigated both experimentally and numerically. It turned out that the contributions of conduction, radiation and convection to the effective thermal conductivity of SATIS, without the closing elements (49 mWmK), amount to 86.2%, 13.2% and 0.6%, respectively. The angle-dependent short-wave radiation exchange within the LCE has been investigated via ray tracing. At the incidence angle of 19% (design angle), 27% of the radiation within the LCE is absorbed by the absorber plate, resulting in measured and computed total solar energy transmittances of 11.2%/11.7%, respectively. For a typical summer irradiation angle of 60%, 98% of the incident radiation is absorbed by the surfaces at the entrance of the LCE. The corresponding total solar energy transmittance amounts to 2.9%.

Research on feature of thermal performance of integrated composite system

Abstract The aim of this study is to explore the effect of stud on the characteristics of thermal insulation and decoration composite system. Prior research conducted has primarily focused on the insulation material performance aside from the composite system. The theoretical calculation and field measurement method are adopted in this paper to compare the insulation performance for different building envelope systems. By considering the thermal transfer coefficient as the performance indicator, thermal bridge and air cavities of integrated insulation composite system as impact factors are investigated. Firstly, the high insulation performance of the composite system is determined via comparing other systems. Secondly, the thermal bridge issue of the composite system led by stud is subsequently investigated followed by the air cavity influenced element being studied via field measurement, which is caused by stud condition. Final results indicate that the thermal insulation and decoration composite system can achieve a substantial insulation performance. In this case, the corresponding optimal size of studs and air cavity is achieved. Further, scattered layout of air cavities could apparently improve the entire thermal system’s insulated performance. All these studied conclusions can contribute designers to implement this system more accurately.

Global Performance of Sustainable Thermal Insulating Systems with Cork for Building Facades

Rehabilitation of facades may be carried out with the application of External Thermal Insulation Systems (ETICS). Their main contribution is the increase of the energy efficiency of buildings. In the literature, hygrothermal, impact and fire performance studies have been carried out on several systems with different insulation materials, such as expanded polystyrene, mineral wool and extruded polystyrene foam insulation. Due to the growing concern with the environment, systems are being developed with more sustainable and ecological materials, such as ICB (expanded cork). These type of boards are responsible for a negative impact in global warming potential, significantly improving the environmental benefits of their use. As these systems were recently introduced to the market, applications on site are very recent and their behaviour over time still unknown. In this research, the durability and global performance of more sustainable systems (with ICB) were analysed through an experimental campaign and compared with EPS (expanded polystyrene) systems. The results show that the systems with ICB obtained satisfactory global behaviour comparable with the EPS systems. The ICB sustainable systems analysed stood out in acoustic performance.

System design and experimental verification of an internal insulation panel system for large-scale cryogenic wind tunnel

With the rapid development of aerodynamics for high speed aircraft, the flight experiments need to be carried out under ultra-high Reynolds number condition to simulate actual high-speed flight conditions, which puts forward higher requirements for the wind tunnel. Reynolds number increases rapidly as the decrease of the flow temperature because the viscosity of the working gas decreases and the density increases. As a result, a pressurized tunnel at cryogenic temperature can provide real-flight Reynolds numbers. Therefore, cryogenic wind tunnel is one of the best testing facilities to rech ultra-high Reynolds number. The thermal insulation system is crucial for the design and operation of the cryogenic wind tunnel. In this paper, the features of an internal insulation system for the cryogenic wind tunnel are firstly highlighted in comparison with traditional insulation systems. The internal thermal insulation system for the cryogenic wind tunnel is discussed. In order to evaluate the thermal insulation performance, the heat transfer calculation for a typical wind tunnel region with the diameter of two meters is carried out using finite element method based on the analyses of the heat transfer conditions. The averaged heat load from the environment is obtained to optimize the liquid nitrogen consumption during the wind tunnel operation. The thickness of the panel should be 150 mm to reach the design target of averaged heat flux 60 W/m2. Meanwhile, the typical region is constructed according to the new internal insulation system. Cryogenic test is conducted and it is proven that the new internal insulation system could efficiently prevent the environment heat flow and ensure the normal operation of the cryogenic wind tunnel.