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Article
Publication date: 25 June 2019

Seyed Mohammad Mousavi, Omid Ali Akbari, Ghanbarali Sheikhzadeh, Ali Marzban, Davood Toghraie and Ali J. Chamkha

The purpose of this study is two phase modeling of Water/Cu nanofluid forced convection in different arrangements of elliptical tube banks in a two-dimensional space.

Abstract

Purpose

The purpose of this study is two phase modeling of Water/Cu nanofluid forced convection in different arrangements of elliptical tube banks in a two-dimensional space.

Design/methodology/approach

The arrangements of tube banks have been regarded as equal spacing triangle (ES), equilateral triangle (ET) and the rotated square (RS). The obtained results indicate that, among the investigated arrangements, the RS arrangement has the maximum value of heat transfer with cooling fluid. Also, the changes of Nusselt number and the local friction factor are under the influence of three main factors including volume fraction of slid nanoparticles, the changes of fluid velocity parameters on the curved surface of tube and flow separation after crossing from a specified angle of fluid rotation.

Findings

In Reynolds number of 250 and in all arrangements of the tube banks, the behavior of Nusselt number is almost the same and the separation of flow happens in almost 155-165 degrees from fluid rotation on surface. In RS arrangement, due to the strength of vortexes after fluid separation, better mixture is created and because of this reason, after the separation zone, the level of local Nusselt number graph enhances significantly.

Originality/value

In this research, the laminar and two-phase flow of Water/Cu nanofluid in tube banks with elliptical cross section has been numerically investigated in a two-dimensional space with different longitudinal arrangements. In this study, the effects of using nanofluid, different arrangements of tube banks and the elliptical cross section on heat transfer and cooling fluid flow among the tube banks of heat exchanger have been numerically simulated by using finite volume method.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 30 no. 4
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 3 August 2015

Motahareh Mokhtari Yazdi, Mohammad Sheikhzadeh and Seyed Ehsan Chavoshi

The purpose of this paper is to identify and evaluate the potential cooling contribution provided by a phase change material cooling vest as part of the total heat…

Abstract

Purpose

The purpose of this paper is to identify and evaluate the potential cooling contribution provided by a phase change material cooling vest as part of the total heat exchange mechanism of the body and take in to account the negative side effects of wearing the cooling garments.

Design/methodology/approach

In this study, the three-part system of body-garment-environment has been simulated through the finite element method and the problem of heat exchange between these three parts has been solved with the help of computer modeling.

Findings

The results of this modeling showed that a large percentage of the cooling efficiency of cooling vest was neutralized by the negative effects of the vest that are weight, lack of breathability, and the effects on the thermal conductivity of the skin. Therefore, the net efficiency of the cooling vests resulted in a lower decrease in skin temperature compared to the state that the negative side effects were not included in the model.

Originality/value

Cooling power obtained with the help of cooling garments have been studied in previous studies using either human tests or manikins. But, what has been addressed less in previous studies relates to the negative effects of such equipment on the comfort of body, along with their cooling effect. So it is the first time witch the effect of side effects of such equipments are studied. Also modeling the real performance of cooling garments have not been done yet.

Details

International Journal of Clothing Science and Technology, vol. 27 no. 4
Type: Research Article
ISSN: 0955-6222

Keywords

Article
Publication date: 17 July 2018

Kai Yang, Mingli Jiao, Sifan Wang, Yuanyuan Yu, Quan Diao and Jian Cao

The purpose of this paper is to investigate thermoregulation properties of different composite phase change materials (PCMs), which could be used in the high temperature…

Abstract

Purpose

The purpose of this paper is to investigate thermoregulation properties of different composite phase change materials (PCMs), which could be used in the high temperature environmental conditions to protect human body against the extra heat flow.

Design/methodology/approach

Three kinds of composite PCM samples were prepared using the selected pure PCMs, including n-hexadecane, n-octadecane and n-eicosane. The DSC experiment was performed to get the samples’ phase change temperature range and enthalpy. The simulated high temperature experiments were performed using human arms in three different high temperature conditions (40°C, 45°C, 50°C), and the skin temperature variation curves varying with time were obtained. Then a comprehensive index TGP was introduced from the curves and calculated to evaluate the thermoregulation properties of different composite PCM samples comprehensively.

Findings

Results show that the composite PCM samples could provide much help to the high temperature human body. It could decrease the skin temperature quickly in a short time and it will not cause the over-cooling phenomenon. Comparing with other two composite PCM samples, the thermoregulation properties of the n-hexadecane and n-eicosane composite PCM is the best.

Originality/value

Using the n-hexadecane and n-eicosane composite PCM may provide people with better protection against the high temperature conditions, which is significative for the manufacture of functional thermoregulating textiles, garments or equipments.

Details

International Journal of Clothing Science and Technology, vol. 30 no. 4
Type: Research Article
ISSN: 0955-6222

Keywords

Article
Publication date: 12 April 2022

Yingsi Wu, Kai Yang Thum, Hui Ting Yong, Aleksander Gora, Alfred Iing Yoong Tok and Vitali Lipik

Personal thermal management in functional textiles is in increasing demand for health care, outdoor activity and energy saving. Thus, developing new strategies is highly…

Abstract

Purpose

Personal thermal management in functional textiles is in increasing demand for health care, outdoor activity and energy saving. Thus, developing new strategies is highly desired for radiative cooling and/or heating by manipulation of the transmissivity, reflectivity and absorptivity of the textiles within solar energy and human body heat radiation ranges.

Design/methodology/approach

Inorganic additives including TiO2, Fe2O3, carbon black (CB), graphene and mica were incorporated into polymer films. The inorganic additives' full spectrum properties and thermal responses were comprehensively investigated.

Findings

The CB composite film showed the highest absorptivity over the full solar to human body radiation spectrum. The mica-white (mica-w) (mica coated with TiO2) and mica-red (mica-r) (mica coated with Fe2O3) composites showed the lowest solar energy absorptivity and a strong body heat radiation reflectivity. Furthermore, according to composites' thermal responses to the simulated solar and human body radiations, CB and mica are promising for both cooling and heating when applied in dual-functional thermal management textiles.

Research limitations/implications

Research has limitation related the amount of additives which can be added to textile. When powder is added to polyester yarn, the amount is limited by 2–3%. When powder is added to the composite which is used for printing, the amount of powder is limited by 5%.

Practical implications

A lot of apparel, especially sport apparel, contains prints. Decoration is one part of print application. Now, a lot of companies work under development of different additives, which provide additional properties to apparel. The closest targets for powder added to prints are cooling and heat retention. Quite often, inorganic additives possess dual properties: the inorganic additives may be heat reflective which his needed for heat retention, but may have high-thermal conductivity, which works well for cooling. Human body has complicated mechanism of heat exchange: convection, radiation and moisture evaporations play main role. The same additive may be cooling if there is a contact with skin but may be heating (IR reflective) if placed in the second or third layer. Thus, effect is needed to be studied first before real application.

Originality/value

This work could provide a comprehensive guideline for the rational design and application of thermal management composite textile materials by revealing the full solar to human body radiation performance of a series of inorganic materials.

Details

International Journal of Clothing Science and Technology, vol. 34 no. 4
Type: Research Article
ISSN: 0955-6222

Keywords

Article
Publication date: 4 July 2016

Albert P.C. Chan, Wen Yi and Francis K.W. Wong

Extreme hot environments are prevalent in many occupational settings, and facilities management workers are no exception. Wearing suitable cooling garment is a useful…

545

Abstract

Purpose

Extreme hot environments are prevalent in many occupational settings, and facilities management workers are no exception. Wearing suitable cooling garment is a useful means to alleviate heat strain and improving performance at heat exposure. This paper aims to evaluate the effectiveness and applicability of the cooling vest across four selected fields (i.e. construction, outdoor cleaning and horticulture, kitchen work and work involved manual handling at the airport) and identify the shortcomings of the cooling vest used by the participating workers.

Design/methodology/approach

This study adopted a two-phase design: a quantitative questionnaire survey followed by qualitative in-depth interviews.

Findings

A remarkable physical strain alleviation (PSA) of 21.1 per cent (14.8 per cent in construction, 18.8 per cent in horticulture and cleaning, 27.4 per cent in kitchen and catering and 26.5 per cent in airport apron service) is achieved by the use of cooling vest in four industries. Despite the success of PSA, several shortcomings of the cooling vest were identified: easily stained color, heavy weight, short cooling time, inflexibility that presents a hazard around moving equipment, lack of industry-specific design, nondurable and thick fabric with poor permeability.

Originality/value

The findings of the current study do not only confirm the effectiveness of the cooling vest in alleviating heat strain and physical strain but also identify the major shortcomings upon which further improvements can be made.

Details

Facilities, vol. 34 no. 9/10
Type: Research Article
ISSN: 0263-2772

Keywords

Article
Publication date: 17 April 2019

Erfan Khodabandeh, Davood Toghraie, A. Chamkha, Ramin Mashayekhi, Omidali Akbari and Seyed Alireza Rozati

Increasing heat transfer rate in spiral heat exchangers is possible by using conventional methods such as increasing number of fluid passes and counter flowing. In…

Abstract

Purpose

Increasing heat transfer rate in spiral heat exchangers is possible by using conventional methods such as increasing number of fluid passes and counter flowing. In addition, newer ideas such as using pillows as baffles in the path of cold and hot fluids and using nanofluids can increase heat transfer rate. The purpose of this study is to simulate turbulent flow and heat transfer of two-phase water-silver nanofluid with 0-6 Vol.% nanoparticle concentration in a 180° path of spiral heat exchanger with elliptic pillows.

Design/methodology/approach

In this simulation, the finite volume method and two-phase mixture model are used. The walls are subjected to constant heat flux of q″ = 150,000 Wm−2. The inlet fluid enters curves path of spiral heat exchanger with uniform temperature Tin = 300 K. After flowing past the pillows and traversing the curved route, the working fluid exchanges heat with hot walls and then exits from the section. In this study, the effect of radiation is disregarded because of low temperature range. Also, temperature jump and velocity slipping are disregarded. The effects of thermophoresis and turbulent diffusion on nanofluid heat transfer are disregarded. By using finite volume method and two-phase mixture model, simulations are performed.

Findings

The results show that the flow and heat transfer characteristics are dependent on the height of pillows, nanoparticle concentration and Reynolds number. Increasing Reynolds number, nanoparticle concentration and pillow height causes an increase in Nusselt number, pressure drop and pumping power.

Originality/value

Turbulent flow and heat transfer of two-phase water-silver nanofluid of 0-6 per cent volume fraction in a 180° path of spiral heat exchanger with elliptic pillows is simulated.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 30 no. 4
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 3 June 2019

Mahdi Ashoori, Ghanbarali Sheikhzadeh and Soroush Sadripour

The purpose of this study is to analyze the effect of using a ceiling fan with central heating system in the winter on thermal comfort and heat transfer rate in a…

Abstract

Purpose

The purpose of this study is to analyze the effect of using a ceiling fan with central heating system in the winter on thermal comfort and heat transfer rate in a three-dimensional numerically.

Design/methodology/approach

The geometry had certain dimensions, and an occupant was modeled to be in the room. In models which were used, the flow was turbulent, and turbulence models were used for simulating turbulence. Between all the models, k-ε model had best matching.

Findings

Results show that using the ceiling fan during the winter had an efficient and considerable effect on improving the thermal comfort and energy saving inside buildings. By the use of ceiling fan, the effective room temperature has increased by 2.5°C. Furthermore, results show that by using ceiling fan in the winter, the predicted mean vote and the predicted percentage dissatisfied indexes improved. At the end, the case Room 11-0.05-15 with temperature of 87°C for radiator and normal fan velocity of o.25m/s were the optimal model that caused the complete thermal comfort and reduced energy consumption up to 28 per cent.

Originality/value

In the present study, the effects of using the ceiling fans on human comfort condition and heat transfer field during the winter (heating system) are studied. Following are the goals for all models: getting the appropriate temperature for radiator so that thermal comfort condition can be applied at the height of 75 cm of the room, velocity for fan so that air speed can be 0.25m/s at the height of 2 m or lower of the room and position to place the fan.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 29 no. 10
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 25 June 2019

Marjan Goodarzi, Iskander Tlili, Zhe Tian and Mohammad Reza Safaei

This study aims to model the nanofluid flow in microchannel heat sinks having the same length and hydraulic diameter but different cross-sections (circular, trapezoidal…

Abstract

Purpose

This study aims to model the nanofluid flow in microchannel heat sinks having the same length and hydraulic diameter but different cross-sections (circular, trapezoidal and square).

Design/methodology/approach

The nanofluid is graphene nanoplatelets-silver/water, and the heat transfer in laminar flow was investigated. The range of coolant Reynolds number in this investigation was 200 ≤ Re ≤ 1000, and the concentrations of nano-sheets were from 0 to 0.1 vol. %.

Findings

Results show that higher temperature leads to smaller Nusselt number, pressure drop and pumping power, and increasing solid nano-sheet volume fraction results in an expected increase in heat transfer. However, the influence of temperature on the friction factor is insignificant. In addition, by increasing the Reynolds number, the values of pressure drop, pumping power and Nusselt number augments, but friction factor diminishes.

Research limitations/implications

Data extracted from a recent experimental work were used to obtain thermo-physical properties of nanofluids.

Originality/value

The effects of temperature, microchannel cross-section shape, the volume concentration of nanoparticles and Reynolds number on thermal and hydraulics behavior of the nanofluid were investigated. Results are presented in terms of velocity, Nusselt number, pressure drop, friction loss and pumping power in various conditions. Validation of the model against previous papers showed satisfactory agreement.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 30 no. 1
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 17 June 2019

Behrouz Mozafari, Ali Akbar Abbasian Arani, Ghanbar Ali Sheikhzadeh and Mahmoud Salimi

The purpose of this paper is to study the effects of using different Brownian models on natural and mixed convection fluid flow and heat transfer inside the square…

Abstract

Purpose

The purpose of this paper is to study the effects of using different Brownian models on natural and mixed convection fluid flow and heat transfer inside the square enclosure filled with the AlOOH–water nanofluid.

Design/methodology/approach

Due to fulfill of this demand, five different models for the effective thermal conductivity and viscosity of the nanofluid are considered. The following results are presented for the Ra=107 to 1010 and Ri=0.01 to 100, whereas the volume fraction of the nanoparticles is varied from φ = 0.01 to 0.04.

Findings

According to the obtained results, increasing of Rayleigh number and reduction of Richardson number leads to the higher values of the average Nusselt number and entropy generation. Also, it is realized that, variation trend of the average Nusselt number and entropy generation in all cases is increasing by growing the volume fraction. It is found that the obtained average Nusselt numbers and entropy generations with Koo and Kleinstreuer are the highest among all the studied cases, and it is followed by Patel, Vajjha and Das, Corcione and Maxwell–Brinkman models, respectively.

Originality/value

Based on the results of present investigation, the Nusselt number difference predicted between the Maxwell–Brinkman model (as constant-property model) and Koo and Kleinstreuer model is about 7.84 per cent at 0.01 per cent volume fraction and 5.47 per cent at 0.04 per cent volume fraction for the Rayleigh number equal to 107. The entropy generation difference predicted between the two above studied model is about 8.05 per cent at 0.01 per cent volume fraction and 5.86 per cent at 0.04 per cent volume fraction for the Rayleigh number equal to 107. It is observed that using constant-property model has a significant difference in the obtained results with the results of other variable-property models.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 30 no. 5
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 13 June 2019

Zhe Tian, Seyed Amin Bagherzadeh, Kamal Ghani, Arash Karimipour, Ali Abdollahi, Mehrdad Bahrami and Mohammad Reza Safaei

This paper aims to propose a new nonlinear function estimation fuzzy system as a novel statistical approach to estimate nanofluids’ thermal conductivity.

Abstract

Purpose

This paper aims to propose a new nonlinear function estimation fuzzy system as a novel statistical approach to estimate nanofluids’ thermal conductivity.

Design/methodology/approach

A fuzzy system having a product inference engine, a singleton fuzzifier, a center average defuzzifier and Gaussian membership functions is proposed for this purpose.

Findings

Results indicate that the proposed fuzzy system can predict the thermal conductivity of Al2O3/paraffin nanofluid with appropriate precision and generalization and it also outperforms the classic interpolation methods.

Originality/value

A new nonlinear function estimation fuzzy system was introduced as a novel statistical approach to estimate nanofluids’ thermal conductivity for the first time.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 30 no. 6
Type: Research Article
ISSN: 0961-5539

Keywords

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