scholarly journals An Experimental Study on the Drying-Out Ability of Highly Insulated Wall Structures with Built-In Moisture and Rain Leakage

2019 ◽  
Vol 9 (6) ◽  
pp. 1222 ◽  
Author(s):  
Klaus Viljanen ◽  
Xiaoshu Lu
Keyword(s):  
Energy Efficient ◽  
Moisture Transfer ◽  
Mineral Wool ◽  
Rain Event ◽  
Controversial Issues ◽  
Wall Structures ◽  
Hygrothermal Performance ◽  
The Difference ◽  
Wood Frame ◽  
Heat And Moisture

The recent research on highly insulated structures presents controversial conclusions on risks in moisture safety. This paper addresses these controversial issues through investigating the hygrothermal performance of energy efficient envelope structures under high moisture loads. The experiments consist of built-in moisture and rain leakage tests in mineral wool insulated structures. A heat and moisture transfer simulation model is developed to examine the drying-out ability in both warm and cold seasons. The results show that the energy efficient structures have an excellent drying out ability against built-in and leakage moisture. The difference in the drying ability is limited compared to conventional structures. A critical leakage moisture amount reaching the insulation cavity for a wood frame wall is determined to be between 6.9–20.7 g in a single rain event occurring every other day. Further research is required to target highly insulated structures, particularly addressing water vapor diffusion and convection.

scholarly journals Numerical Network Modeling of Heat and Moisture Transfer through Capillary-Porous Building Materials

Materials ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 1819
Author(s):  
Borys Basok ◽  
Borys Davydenko ◽  
Anatoliy M. Pavlenko
Keyword(s):  
Building Materials ◽  
Moisture Transfer ◽  
Three Dimensional ◽  
Total Pore Volume ◽  
Equivalent Diameter ◽  
Average Pore ◽  
The Difference ◽  
Three Dimensional Coordinate ◽  
Solid Liquid ◽  
Heat And Moisture

The article presents the modeling of the dynamics of the vapor-gas mixture and heat and mass transfer (sorption-desorption) in the capillary structure of the porous medium. This approach is underpinned by the fact that the porous structure is represented by a system of linear microchannels oriented along the axes of a three-dimensional coordinate system. The equivalent diameter of these channels corresponds to the average pore diameter, and the ratio of the total pore volume to the volume of the entire porous material corresponds to its porosity. The entire channel area is modeled by a set of cubic elements with a certain humidity, moisture content, pressure and temperature. A simulation is carried out taking into account the difference in temperatures of each of the phases: solid, liquid and gas.

scholarly journals Highly Insulated Wall Systems with Exterior Insulation of Polyisocyanurate under Different Facer Materials: Material Characterization and Long-Term Hygrothermal Performance Assessment

Materials ◽  
2020 ◽  
Vol 13 (15) ◽  
pp. 3373 ◽  
Author(s):  
Emishaw Iffa ◽  
Fitsum Tariku ◽  
Wendy Ying Simpson
Keyword(s):  
Performance Assessment ◽  
Control Strategy ◽  
Energy Efficient ◽  
Material Characterization ◽  
Air Leakage ◽  
Material Development ◽  
Hygrothermal Performance ◽  
New Construction ◽  
Wood Frame

The application of exterior insulation in both new construction and retrofits is a common practice to enhance the energy efficiency of buildings. In addition to increased thermal performance, the rigid insulation can serve to keep the sheathing board warm and serve as a water-resistive barrier to keep moisture-related problems due to condensation and wind-driven rain. Polyisocyanurate (PIR) rigid boards have a higher thermal resistance in comparison to other commonly used exterior insulation boards. However, because of its perceived lower permeance, its use as exterior insulation is not very common. In this study, the hygrothermal property of PIR boards with different facer types and thicknesses is characterized. The material data obtained through experimental test and extrapolation is used in a long term hygrothermal performance assessment of a wood frame wall with PIR boards as exterior insulation. Results show that PIR with no facer has the smallest accumulated moisture on the sheathing board in comparison to other insulation boards. Walls with a bigger thickness of exterior insulation perform better when no vapor barrier is used. The PIR exterior insulation supports the moisture control strategy well in colder climates in perfect wall scenarios, where there is no air leakage and moisture intrusion. In cases where there is trapped moisture, the sheathing board has a higher moisture content with PIR boards with both aluminum or fiberglass type facers. An innovative facer material development for PIR boards can help efforts targeting improved energy-efficient and durable wall systems.

scholarly journals Assessment of Deterioration Risk of Maijishan Grotto under the Radiation Difference Based on Heat and Moisture Transfer Model

2021 ◽  
Vol 2069 (1) ◽  
pp. 012082
Author(s):  
R B Wu ◽  
Y Ma ◽  
H R Xie ◽  
S Hokoi ◽  
Y Q Yue ◽  
...  
Keyword(s):  
Thermal Stress ◽  
Water Content ◽  
Moisture Transfer ◽  
Transfer Model ◽  
Two Dimensional ◽  
Architectural Heritage ◽  
Direct Sunlight ◽  
The Difference ◽  
The Buddha ◽  
Heat And Moisture

Abstract The ambient environment of architectural heritage is an important factor affecting its conservation. Two adjacent rows of Buddha statues in Grottoes No. 3 (semi-open) of Maijishan Grotto in Gansu, China, show apparent differences in the degree of deterioration. This study made a monitoring scheme of grottoes microenvironments such as air temperature, relative humidity, radiation, and surface temperature to explore the cause of the difference. A two-dimensional heat and moisture (HAM) transfer model was established and verified to simulate the temperature and humidity on the surface and inside of the Buddha statues. Then, temperature and water content fluctuation and the risks of thermal stress destruction on the surface and near the surface of the Buddha statues were evaluated. The results show that the radiation difference causes thermal stress and water content differences both in heights and in depths. This impact brought by the direct sunlight may contribute to the different deterioration on the two rows of Buddha statues. The eaves shaded the upper row of the Buddha statues much longer than the lower ones. Less severe fluctuation and differences in temperature and water content occur at the middle and upper points. This study evaluates the degradation of Grottoes No. 3 and has guiding significance for its preservation methods.

Coupled transient heat and moisture transfer investigation of facade panel connections

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Bahram Abediniangerabi ◽  
Mohsen Shahandashti ◽  
Atefe Makhmalbaf
Keyword(s):  
Moisture Transfer ◽  
The Other ◽  
Heat Transfer Analysis ◽  
Thermal Resistivity ◽  
Heat And Moisture Transfer ◽  
Maximum Heat ◽  
Content Type ◽  
Hygrothermal Performance ◽  
Coupled Heat And Moisture ◽  
Heat And Moisture

Purpose The purpose of this study is to investigate the effect of panel connections on the hygrothermal performance of facade panels using a coupled, transient heat and moisture transfer analysis. Design/methodology/approach A coupled, transient heat and moisture transfer analysis has been conducted to investigate the effect of panel connections in the hygrothermal behavior of facade panels. Governing partial differential equations for the coupled heat and moisture transfer were formulated. Four panel connections proposed by pre-cast/pre-stressed concrete institute were modeled for the ultra-high performance fiber-reinforced concrete facade panel as illustrations and a finite element method was used to solve the numerical models. Findings The results of heat transfer analysis showed that steel connections could significantly reduce the thermal resistivity of facade panels by converging heat fluxes and acting as thermal bridges within facade panels. The results also showed that the maximum heat flux in the steel connector of the panel to foundation connection was 10 times higher compared to the other connections. Also, the results of moisture transfer showed that air gaps between the panels had higher moisture flux compared to the other layers in the models. The results show the significant importance of panel connections in the energy performance analysis of facade systems. They also highlight the importance of devising novel connection designs and materials that consider the transient, coupled heat and moisture transfer in the connections to effectively exploit the potential opportunities provided by innovative facade systems to improve building energy efficiency. Originality/value This paper, for the first time, investigates the effect of panel connections in the hygrothermal performance of building facade systems using a coupled, transient heat and moisture transfer analysis.

scholarly journals Global warming potential of building constructions based on heat and moisture transport analysis

2021 ◽  
pp. 278-278
Author(s):  
Balázs Nagy ◽  
Martin Marosvölgyi ◽  
Zsuzsa Szalay
Keyword(s):  
Global Warming ◽  
Thermal Insulation ◽  
Global Warming Potential ◽  
Energy Demand ◽  
Moisture Transfer ◽  
Mineral Wool ◽  
Building Construction ◽  
Additional Information ◽  
Operational Energy ◽  
Heat And Moisture

Global Warming Potential (GWP) is one of the most important Life Cycle Assessment (LCA) indicator, which shows how much heat a greenhouse gas traps in the atmosphere relative to carbon dioxide. In this study, we calculated the GWP of a highly insulated building construction detail of a residential nearly-zero energy building (nZEB) based on numerical simulations. To calculate the heat loss of building constructions, which is necessary for estimating the operational energy demand in the use phase of the building, we compared two numerical simulation methods: 2D thermal simulations and 2D conjugated heat and moisture transfer (HAM) simulations. Besides that, we compared the effect of selecting different thermal insulation materials for insulating the building constructions, such as EPS, mineral wool and wood wool. We then compared the thermal and linear thermal transmittances from the simulations besides evaluating the moisture transmittance behaviour of the constructions. In all examined scenarios, the constructions with mineral wool ended up being the highest impact alternative, while EPS was the lowest for walls and wood wool was for wall corner joints. We also found that including the wall corner joints in GWP calculations could increase the overall GWP of an average-sized family house by 10%. Our study shows the HAM induced differences between thermal insulations, and demonstrates that HAM modelling-based LCA of building construction details gives valuable additional information to designers to choose the proper thermal insulation.

scholarly journals ON MODELLING HEAT AND MOISTURE TRANSFER IN SANDWICH WALL AND SLAB STRUCTURES

2006 ◽  
Vol 12 (4) ◽  
pp. 337-343 ◽  
Author(s):  
Vadim Nikitin ◽  
Andrzej Lapko
Keyword(s):  
Moisture Transfer ◽  
Ambient Air ◽  
Thermal Engineering ◽  
Computational Accuracy ◽  
Heat And Moisture Transfer ◽  
Moisture Migration ◽  
Wall Structures ◽  
Sandwich Wall ◽  
Heat And Moisture ◽  
Unsteady Processes

In real wall or slab structures made of capillary‐porous materials (such as masonry or concrete) exposed to ambient air, the unsteady processes of heat transfer and moisture migration as reciprocal phenomena are observed. Basing on the Fourier general differential equations and using the assumptions of the elementary heat balance method, the problem of heat and moisture transfer has been studied in multi‐layer wall structures, such as sandwich panels. As a result the general equations were proposed and transformed into formulas useful in the FDM approach (Finite Difference Method). On this basis a computer program was written to analyse the phenomena mentioned above. Some computational tests for a concrete sandwich panel wall with insulation made of foamed polyurethane were presented and discussed to illustrate a possible application of this approach. The paper shows that the improvement of computational accuracy of modelling the thermal engineering problems requires an assumption of real parameters which characterise capillary‐porous structural materials and result from moisture transfer.

scholarly journals Energy and hygrothermal performance of builtin mineral wool thermal insulations

2018 ◽  
Vol 163 ◽  
pp. 08001 ◽  
Author(s):  
Balázs Nagy ◽  
Tamás K. Simon
Keyword(s):  
Energy Performance ◽  
Mineral Wool ◽  
Single Family ◽  
Energy Meter ◽  
Dwelling House ◽  
Measurement Results ◽  
Hygrothermal Performance ◽  
Design Values ◽  
Heat And Moisture ◽  
Thermal Insulations

The paper analyses the monitoring measurement results on energy performance and hygrothermal behaviour of built-in rock and glass mineral wool thermal insulations in an energy efficiently refurbished typical single-family dwelling house in Hungary. The experimental monitoring measurements included an external weather station; internal air condition measurements; temperature, relative humidity and heat flux sensors in the layers of the facade and attic. An energy meter was installed into the heating systems. Apart from the insulated one, the energy consumption of an uninsulated but identical family house close by to the refurbished one was monitored as control. In the paper, apart from comparing the energy performance of the monitored buildings, the conjugated heat and moisture behaviour of the built-in mineral wool insulations were examined and compared to their design values and conditions. The temperature and moisture correction factors were evaluated. The paper presents laboratory measurements on the thermal conductivity of built-in and etalon mineral wool insulation samples also. The circumstances were set according to the experienced built-in conditions in the monitored buildings and compares the energy and hygrothermal performance of new and aged insulations.

The Shikani HME: A New Tracheostomy Heat and Moisture Exchanger

2020 ◽  
Vol 63 (9) ◽  
pp. 2921-2929
Author(s):  
Alan H. Shikani ◽  
Elamin M. Elamin ◽  
Andrew C. Miller
Keyword(s):  
Ex Vivo ◽  
Moisture Loss ◽  
Speaking Valve ◽  
Time Zero ◽  
In Series ◽  
Turbulent Airflow ◽  
The Difference ◽  
Loss Efficiency ◽  
Heat And Moisture ◽  
Lung Simulation

Purpose Tracheostomy patients face many adversities including loss of phonation and essential airway functions including air filtering, warming, and humidification. Heat and moisture exchangers (HMEs) facilitate humidification and filtering of inspired air. The Shikani HME (S-HME) is a novel turbulent airflow HME that may be used in-line with the Shikani Speaking Valve (SSV), allowing for uniquely preserved phonation during humidification. The aims of this study were to (a) compare the airflow resistance ( R airflow ) and humidification efficiency of the S-HME and the Mallinckrodt Tracheolife II tracheostomy HME (M-HME) when dry (time zero) and wet (after 24 hr) and (b) determine if in-line application of the S-HME with a tracheostomy speaking valve significantly increases R airflow over a tracheostomy speaking valve alone (whether SSV or Passy Muir Valve [PMV]). Method A prospective observational ex vivo study was conducted using a pneumotachometer lung simulation unit to measure airflow ( Q ) amplitude and R airflow , as indicated by a pressure drop ( P Drop ) across the device (S-HME, M-HME, SSV + S-HME, and PMV). Additionally, P Drop was studied for the S-HME and M-HME when dry at time zero (T 0 ) and after 24 hr of moisture testing (T 24 ) at Q of 0.5, 1, and 1.5 L/s. Results R airflow was significantly less for the S-HME than M-HME (T 0 and T 24 ). R airflow of the SSV + S-HME in series did not significant increase R airflow over the SSV or PMV alone. Moisture loss efficiency trended toward greater efficiency for the S-HME; however, the difference was not statistically significant. Conclusions The turbulent flow S-HME provides heat and moisture exchange with similar or greater efficacy than the widely used laminar airflow M-HME, but with significantly lower resistance. The S-HME also allows the innovative advantage of in-line use with the SSV, hence allowing concurrent humidification and phonation during application, without having to manipulate either device.

Mathematical Models of Papermaking

2001 ◽  
Vol 6 (1) ◽  
pp. 9-19 ◽  
Author(s):  
A. Buikis ◽  
J. Cepitis ◽  
H. Kalis ◽  
A. Reinfelds ◽  
A. Ancitis ◽  
...  
Keyword(s):  
Mathematical Model ◽  
Initial Value Problems ◽  
Moisture Transfer ◽  
Bound Water ◽  
Drying Process ◽  
Initial Value ◽  
First Order ◽  
Heat And Moisture ◽  
The Mathematical Model ◽  
The Web

The mathematical model of wood drying based on detailed transport phenomena considering both heat and moisture transfer have been offered in article. The adjustment of this model to the drying process of papermaking is carried out for the range of moisture content corresponding to the period of drying in which vapour movement and bound water diffusion in the web are possible. By averaging as the desired models are obtained sequence of the initial value problems for systems of two nonlinear first order ordinary differential equations. 

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