Multi-objective optimization of heat transfer mechanisms of microcellular polymeric foams from thermal-insulation point of view

Hasanzadeh, Rezgar; Azdast, Taher; Doniavi, Ali; Lee, Richard Eungkee

doi:10.1016/j.tsep.2018.11.002

Cited by 75 publications

(35 citation statements)

References 62 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Because of the very small cell size of the foams under study (600–300 μm) the convective mechanism ( λ c ) can be considered negligible . The conductive terms of the gas and the solid phases can be estimated using

λ^{normalg} = λ_{normalg} V_{normalg}

λ^{normals} = λ_{normals} \frac{V_{s}}{3} [f_{normals} \sqrt{A} + 2 (1 - f_{normals}) A^{1 / 4}]

where V g is the volume fraction of the gas phase (1 – ρ r ), V s is the volume fraction of the solid phase ( ρ r ), A is the AR, λ g is the thermal conductivity of the gas mixture and λ s is the thermal conductivity of solid PU (0.26 W mK –1 ) .…”

Section: Resultsmentioning

confidence: 99%

“…The thermal conductivity is determined by the following heat transfer mechanisms: conduction along the solid phase ( λ s ), conduction through the gas phase ( λ g ), thermal radiation ( λ r ) and convection within the cells ( λ c ). The latter is negligible for foams with small cell sizes (less than 2 mm) . The thermal conductivity of RPU foams depends mainly on the types and amount of blowing agents contained in the closed cells, due to the high contribution of λ g of the gas mixture to the total thermal conductivity (higher than 60%) .…”

Section: Introductionmentioning

confidence: 99%

“…The latter is negligible for foams with small cell sizes (less than 2 mm) . The thermal conductivity of RPU foams depends mainly on the types and amount of blowing agents contained in the closed cells, due to the high contribution of λ g of the gas mixture to the total thermal conductivity (higher than 60%) . Thus, the use of blowing agents with low thermal conductivities is one of the key strategies to improve the thermal properties of RPU foams.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Long‐term thermal conductivity of cyclopentane–water blown rigid polyurethane foams reinforced with different types of fillers

Santiago‐Calvo

Tirado‐Mediavilla

Ruiz‐Herrero

et al. 2019

Polymer International

View full text Add to dashboard Cite

An understanding of the long‐term thermal conductivity of rigid polyurethane (RPU) foams presents great interest in the building field considering the conservation of energy efficiency. In this study, the effect of different types of particles (talc, diatomaceous earth and non‐porous silica) on the thermal conductivity of RPU foams blown with cyclopentane and water as blowing agents was investigated during 3 years of aging. The characterization of the cellular structure shows how the addition of particles causes a cell size reduction of the foams, and consequently an enhancement of the thermal properties just after production. However, this initial reduction is not maintained, because each foam shows a different thermal conductivity evolution with time. We have found, for the first time, a relationship between the slope of the thermal conductivity versus time at the first measurements and the internal temperature reached during the foaming process. The evolution of the RPU foams in which higher internal temperatures were reached is more pronounced than in those RPU foams where lower foaming temperatures were observed. This effect is related to the kinetics of the diffusion of the gas occluded inside the cells and imposes a new criterion for the selection of particles to reduce the thermal conductivity of RPU foams; these additives should ideally decrease the temperature reached during the foaming process. Moreover, the effect of aging on the thermal conductivity is explained by using theoretical models. © 2019 Society of Chemical Industry

show abstract

λ^{normalg} = λ_{normalg} V_{normalg}

λ^{normals} = λ_{normals} \frac{V_{s}}{3} [f_{normals} \sqrt{A} + 2 (1 - f_{normals}) A^{1 / 4}]

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Long‐term thermal conductivity of cyclopentane–water blown rigid polyurethane foams reinforced with different types of fillers

Santiago‐Calvo

Tirado‐Mediavilla

Ruiz‐Herrero

et al. 2019

Polymer International

View full text Add to dashboard Cite

show abstract

“…Besides considering technical issues and providing correct data for engineers, this paper aims to contribute to the general discussion about the thermal transport mechanisms in polymeric insulating materials and better understanding them. Example of such discussions describing mainly EPS insulation can be found in the recognized literature [37][38][39][40][41][42][43][44][45][46][47][48][49]. In particular, it has been reported that, when incorporating industrially higher concentrations of GMP into an EPS polymer matrix, the total thermal conductivity can be reduced by opacifying the insulation product for thermal radiation, which is absorbed by the carbon atoms in graphite or scattered by the larger graphite microparticles.…”

Section: Introductionmentioning

confidence: 99%

Change in Conductive–Radiative Heat Transfer Mechanism Forced by Graphite Microfiller in Expanded Polystyrene Thermal Insulation—Experimental and Simulated Investigations

2020

View full text Add to dashboard Cite

This article introduces an innovative approach to the investigation of the conductive–radiative heat transfer mechanism in expanded polystyrene (EPS) thermal insulation at negligible convection. Closed-cell EPS foam (bulk density 14–17 kg·m−3) in the form of panels (of thickness 0.02–0.18 m) was tested with 1–15 µm graphite microparticles (GMP) at two different industrial concentrations (up to 4.3% of the EPS mass). A heat flow meter (HFM) was found to be precise enough to observe all thermal effects under study: the dependence of the total thermal conductivity on thickness, density, and GMP content, as well as the thermal resistance relative gain. An alternative explanation of the total thermal conductivity “thickness effect” is proposed. The conductive–radiative components of the total thermal conductivity were separated, by comparing measured (with and without Al-foil) and simulated (i.e., calculated based on data reported in the literature) results. This helps to elucidate why a small addition of GMP (below 4.3%) forces such an evident drop in total thermal conductivity, down to 0.03 W·m−1·K−1. As proposed, a physical cause is related to the change in mechanism of the heat transfer by conduction and radiation. The main accomplishment is discovering that the change forced by GMP in the polymer matrix thermal conduction may dominate the radiation change. Hence, the matrix conduction component change is considered to be the major cause of the observed drop in total thermal conductivity of EPS insulation. At the microscopic level of the molecules or chains (e.g., in polymers), significant differences observed in the intensity of Raman spectra and in the glass transition temperature increase on differential scanning calorimetry(DSC) thermograms, when comparing EPS foam with and without GMP, complementarily support the above statement. An additional practical achievement is finding the maximum thickness at which one may reduce the “grey” EPS insulating layer, with respect to “dotted” EPS at a required level of thermal resistance. In the case of the thickest (0.30 m) panels for a passive building, above 18% of thickness reduction is found to be possible.

show abstract

“…Polymeric foams find diverse applications owning to their high specific impact strength, high specific modulus, high specific hardness, and excellent sound and thermal insulation properties . Apart from structural applications, polymeric foams are also explored as suitable candidates for biomedical and tissue engineering applications.…”

Section: Introductionmentioning

confidence: 99%

Poly(vinyl alcohol) foams reinforced with carbon nanotubes for stapedial annular ligament applications

Bhinder

Agnihotri

2019

J of Applied Polymer Sci

View full text Add to dashboard Cite

This study aims to develop carbon nanotubes (CNTs) reinforced poly(vinyl alcohol) (PVA) foams as a possible material for stapedial annular ligament (SAL) application. As-grown (AG) and purified CNTs are used as reinforcing fillers for PVA foams. Uniaxial and cyclic compression tests reveal that specific modulus and energy dissipation behavior improve after reinforcing foam with CNTs. A relatively higher improvement in specific modulus is recorded for purified CNTs as they tend to produce stiffer cell walls. Thermogravimetric analysis shows thermal stability improves after addition of CNTs in PVA foams. The 50 wt % degradation temperature is higher for PVA_AG foam in comparison to neat PVA foam. Under dynamic loading storage, modulus is found to be higher for CNT doped foams with higher relative improvement with purified CNTs than AG CNTs. It is shown that reinforcing PVA foams with purified CNTs is a feasible strategy to improve their average mechanical properties and microstructure for SAL application. While the specific elastic modulus of neat PVA foam found to be in range of 0.05-0.06 MPa gcc −1 with almost zero porosity. The addition of CNTs provides a wide range of specific elastic modulus 0.1-1.3 MPa gcc −1 with an average pores size of about 300 μm.

show abstract

Multi-objective optimization of heat transfer mechanisms of microcellular polymeric foams from thermal-insulation point of view

Cited by 75 publications

References 62 publications

Long‐term thermal conductivity of cyclopentane–water blown rigid polyurethane foams reinforced with different types of fillers

Long‐term thermal conductivity of cyclopentane–water blown rigid polyurethane foams reinforced with different types of fillers

Change in Conductive–Radiative Heat Transfer Mechanism Forced by Graphite Microfiller in Expanded Polystyrene Thermal Insulation—Experimental and Simulated Investigations

Poly(vinyl alcohol) foams reinforced with carbon nanotubes for stapedial annular ligament applications

Contact Info

Product

Resources

About