Moisture Diffusion Characteristics of a Paper Membrane Used for a Cross Flow Enthalpy Exchanger

2018 ◽  
Vol 26 (03) ◽  
pp. 1850023
Author(s):  
Nae-Hyun Kim
Keyword(s):  
Diffusion Coefficient ◽  
Indoor Air ◽  
Moisture Transfer ◽  
Cross Flow ◽  
Moisture Diffusion ◽  
Outdoor Temperature ◽  
Diffusion Characteristics ◽  
Wide Range ◽  
Heat And Moisture ◽  
Indoor And Outdoor

An enthalpy exchanger is the key component of an enthalpy recovery ventilator, which is installed in apartments or office buildings to maintain proper indoor air quality. In this study, the performance data of the enthalpy exchanger made of paper membrane were obtained for wide range of temperature and humidity conditions. Using the data, diffusion coefficient correlations were developed through modeling of heat and moisture transfer. The heat transfer effectiveness was relatively constant independent of outdoor temperature condition. On the other hand, the moisture transfer effectiveness was highly dependent on outdoor humidity and temperature. In general, moisture transfer effectiveness increased as relative humidity increased. The moisture transfer effectiveness also increased as temperature difference between indoor and outdoor increased. Moisture diffusion coefficient correlations were developed from the data, which predicted the moisture transfer effectiveness was within [Formula: see text]%.

scholarly journals Numerical modelling of a hemp concrete wall

2019 ◽  
Vol 85 ◽  
pp. 08003 ◽  
Author(s):  
Georges Costantine ◽  
Chadi Maalouf ◽  
Tala Moussa ◽  
Guillaume Polidori ◽  
Elias Kinab
Keyword(s):  
Building Materials ◽  
Moisture Transfer ◽  
Numerical Study ◽  
Object Oriented ◽  
Hysteresis Phenomenon ◽  
Energy Costs ◽  
Concrete Wall ◽  
Heat And Moisture ◽  
Account Heat ◽  
Indoor And Outdoor

In a global warming context associated to the abuse of energy consumption, actual researches focus more and more on reducing energy costs in the building sector. This target could be achieved by using innovative building materials, such as hemp concrete, due to its positive impacts on thermal and environmental levels. The aim of this work is to carry out a numerical study of a hemp concrete wall subjected to several indoor and outdoor conditions of temperature and relative humidity using the program object oriented SPARK. The hygrothermal behaviour of the wall is investigated taking into account heat and moisture transfer within the wall as well as hysteresis phenomenon between the sorption and desorption curves and their temperature dependency.

HEAT AND MOISTURE TRANSFER CHARACTERISTICS OF A PLATE-TYPE ENTHALPY EXCHANGER MADE OF PAPER

2011 ◽  
Vol 19 (01) ◽  
pp. 85-92 ◽  
Author(s):  
EUL-JONG LEE ◽  
NAE-HYUN KIM ◽  
GIL-SUB SONG ◽  
JUNG-PYO LEE
Keyword(s):  
Relative Humidity ◽  
Water Content ◽  
Moisture Transfer ◽  
Effect Of Temperature ◽  
Heat And Moisture Transfer ◽  
Equilibrium Water Content ◽  
Content Ratio ◽  
Heat And Moisture ◽  
Plate Type ◽  
Indoor And Outdoor

In this study, heat and moisture transfer data of an enthalpy exchanger were obtained varying the indoor and outdoor condition systematically. At the same time, equilibrium water content ratios of the membrane were measured. It is shown that equilibrium water content ratio of the membrane increases with the increase of relative humidity. The effect of temperature on equilibrium water content ratio, however, is rather complex. It decreases with the increase of temperature to a certain value, and then increases with further increase of temperature. Moisture transfer effectiveness of the enthalpy exchanger is also affected by relative humidity and temperature. Heat transfer effectiveness, however, is independent of relative humidity and temperature. Moisture transfer effectiveness of the enthalpy exchanger was successfully correlated by equilibrium water content ratio of the membrane.

Relationships Between Aerosol Particles and Airborne Bacteria and their Dependence on Environmental Factors in a Dairy Calf House

2019 ◽  
Vol 62 (6) ◽  
pp. 1819-1828 ◽  
Author(s):  
Md. Aminul Islam ◽  
Atsuo Ikeguchi ◽  
Takanori Naide
Keyword(s):  
Indoor Air ◽  
Aerosol Particles ◽  
Aerobic Bacteria ◽  
Airborne Bacteria ◽  
Dairy Calf ◽  
Outdoor Temperature ◽  
The Mean ◽  
High Concentrations ◽  
Mean Concentration ◽  
Indoor And Outdoor

Abstract. The quality of indoor air dramatically affects the health of animals and humans. An investigation was conducted into the relationships among the total number of aerosol particles and different types of airborne bacteria and their dependence on indoor and outdoor environmental factors, including air temperature and relative humidity (RH), in the indoor air of a dairy calf house in Tochigi, Japan, during the summer season. The concentrations of aerosol particles, the concentrations of airborne total aerobic bacteria (, , and spp.) in the indoor air, and the indoor and outdoor temperature and RH were evaluated from 14 weekly measurements. The mean concentration of small aerosol particles (0.3 to 2.0 µm) was higher than the mean concentration of large aerosol particles (2.0 to 10.0 µm) in the summer season. The mean concentration of airborne total aerobic bacteria was higher than the concentrations of airborne , , and spp. Airborne and were positively correlated with the number of 2.0 to 10.0 µm aerosol particles, i.e., high concentrations of 2.0 to 10.0 µm particles were correlated with high concentrations of airborne and . Airborne total aerobic bacteria did not correlate with the number of aerosol particles of any size, but spp. was negatively correlated with the number of 1.0 to 2.0 µm aerosol particles, i.e., high concentrations of 1.0 to 2.0 µm particles were correlated with low concentrations of airborne spp. The indoor temperature and indoor and outdoor RH did not correlate with any airborne bacteria. The outdoor temperature was negatively correlated with spp., i.e., high outdoor temperature was correlated with a low concentration of spp. in the indoor air of the dairy calf house. Both indoor and outdoor temperatures were positively correlated with the number of 0.5 to 5.0 µm aerosol particles, and indoor RH was negatively correlated with the number of 5.0 to 10.0 µm aerosol particles. These findings will be important for elucidating the role of aerosol particles in the transmission of airborne bacteria and ultimately for the mitigation of aerosol particles and airborne bacteria in dairy houses. HighlightsThe number of fine aerosol particles increased with increasing temperatures.Environmental factors had a less critical effect on airborne bacteria than aerosol particles.Airborne E. coli strongly positively correlated with 5.0 to 10.0 µm aerosol particles.Airborne Salmonella spp. negatively correlated with 1.0 to 2.0 µm aerosol particles.Relative humidity did not affect any airborne bacteria. Keywords: Aerosol particle number, Airborne bacteria, Dairy calf, Indoor air, Relationship, Summer season.

scholarly journals Numerical investigation on the effect of varying the number of flow dividers on Z-shaped membrane heat exchanger performance

2020 ◽  
Vol 16 (1) ◽  
pp. 85-89
Author(s):  
Mohammad Shakir Nasif ◽  
Ra'fat Al-Waked ◽  
Firas Ismail
Keyword(s):  
Heat Exchanger ◽  
Indoor Air ◽  
Energy Recovery ◽  
Heat Recovery ◽  
Cfd Simulation ◽  
Moisture Transfer ◽  
Flow Distribution ◽  
Building Energy ◽  
Minor Effect ◽  
Heat And Moisture

To reduce building energy consumption and to improve indoor air quality, it is necessary the use heat recovery such as air-to-air fixed-plates enthalpy heat exchanger in mechanical ventilation. Prediction of enthalpy performance by utilizing CFD simulation is challenging since most commercial software do not simulate moisture transfer. In this research, a Z-shaped membrane heat exchanger which is used for building energy recovery systems was modeled by using commercial CFD software (FLUENT). Kraft paper of 45 gsm was used as the heat exchanger heat and moisture transfer surface. A User Define Function (UDF) code was developed and incorporated in the CFD software to enable the software to model moisture transfer through the membrane. This model is used to investigate the performance of Z-Shaped heat exchanger when the number of flow dividers within the heat exchanger is varied. It was found that a 21 % increase in the effectiveness was achieved when the number of ribs was increased from no ribs to 5 ribs. However, increasing the number of ribs from 5 to 11 only demonstrates minor effect. Therefore, no significant improvement is noticed when the number of ribs is increased beyond 5 which is attributed to air flow distribution which because more uniform when number of ribs is increased. However, the flow is already uniform when 5 ribs where used, hence increasing the ribs to 11 will not improve the flow distribution further.

scholarly journals Moisture transport through non-porous hydrophilic membranes used in protective clothing

2013 ◽  
Vol 17 (5) ◽  
pp. 1293-1298 ◽  
Author(s):  
Fang-Long Zhu ◽  
Yu Zhou ◽  
Jian-Xin He
Keyword(s):  
Diffusion Coefficient ◽  
Diffusion Model ◽  
Transfer Process ◽  
Moisture Transfer ◽  
Effective Diffusion ◽  
Moisture Diffusion ◽  
Mass Transfer Process ◽  
Transfer Resistance ◽  
Moisture Diffusion Coefficient ◽  
Effective Moisture

The three-step upright cup method was employed to determine the total moisture transfer resistance and the two air layer resistances on both sides of the membrane. The effective moisture diffusion coefficient in air layer between the membrane and water surface was determined by the regressive method, and the effective moisture diffusion coefficient of membrane was calculated. Experiments were conducted on a non-porous hydrophilic thermoplastic polyester elastomer membrane. The moisture transfer process through the membrane was modeled by using the solution-diffusion model. The effects of membrane microstructure on membrane permeation were analyzed based on the solution-diffusion model and experimental data. The results show that the effective diffusion coefficient can be used to evaluate the mass transfer process through the non-porous hydrophilic thermoplastic polyester elastomer membrane.

Numerical Simulation of Coupled Heat and Moisture Transfer in Porous Building Material

2011 ◽  
Vol 287-290 ◽  
pp. 3106-3111 ◽  
Author(s):  
Xiao Bin Zhang ◽  
Wei Bing Zhu ◽  
Si Peng Tan
Keyword(s):  
Temperature Gradient ◽  
Indoor Air ◽  
Moisture Transfer ◽  
Computer Code ◽  
Building Envelope ◽  
Specific Humidity ◽  
Heat And Moisture Transfer ◽  
Coupled Heat And Moisture ◽  
Heat And Moisture ◽  
The Relationship

Building envelope is a typical porous medium. The internal accumulation of moisture will not only affect the structural strength, but also cause the growth of bacterial in the structure, which can seriously affect the indoor air quality. In this work, the modified Luikov coupled heat and moisture transfer equation is derived by using finite difference method. A FORTRAN computer code is developed based on the supplied experiment conditions. The effect of various parameters (include temperature gradient, sorption isotherm, specific humidity etc.) on the coupled heat and moisture transfer and the relationship between the temperature gradient and the moisture gradient are discussed. The results show that the simulation results agree well with the experimental data.

Evaluation of Classical Models for Thermal and Moisture Transport in Stone Walls of Historical Buildings

2017 ◽  
Vol 21 ◽  
pp. 161-168
Author(s):  
Iuliia Redikultseva ◽  
Dashnor Hoxha ◽  
Naima Belayachi
Keyword(s):  
Moisture Transfer ◽  
Transfer Problem ◽  
Moisture Diffusion ◽  
External Edge ◽  
Diffusive Model ◽  
Classical Models ◽  
Stone Walls ◽  
Heat And Moisture ◽  
Diffusion Problems

This paper concerns the evaluation and the validation of a heat and moisture transfer models in stone walls using in situ measurements on an instrumented wall. Firstly, a pure thermal (respectively moisture) diffusion problems are considerate, then this problem was combined with convection on the external edge of model. It is found that, despite of an uncoupled approach, the nonlinear thermal diffusive model performs quite well and reproduces perfectly the measured temperatures. It is the same for the convective-diffusive thermal problem, where the temperature on the surface wall is also reproduced quite well. An improvement of this second type problem results could be expected by taking into account the radiation. Otherwise, the both cases of moisture transfer problem (purely diffusive or diffusive-convective problem) are ill-simulated by the Kunzel’s model.

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