Experimental investigation of the effects of non-uniform clothing ensembles on the occupants' thermal perceptions under a local ventilation system
Peyman Ebrahimi Naghani, Seyed Alireza Zolfaghari, Mehdi Maerefat, Jorn Toftum, Seyed Mohammad Hooshmand
Journal PapersInternational Journal of Air-Conditioning and Refrigeration , 2021 February 17, {Pages }
Abstract
This paper presents an experimental study that evaluated the effects of three different non-uniform types of clothing ensembles (Type A: short-sleeve shirt, T-shirt underwear, men’s briefs, straight trousers, socks, shoes; Type B: long-sleeve shirt, T-shirt underwear, men’s briefs, straight trousers; and Type C: long-sleeve shirt, men’s briefs, straight trousers, thick socks, shoes) with almost the same thermal insulation (about 0.52 clo) on the subjects’ local and overall thermal sensation and air movement preference under a desktop local ventilation system. The experiment was conducted in a test chamber with the mean air temperature of 24?0.5 C and under three supply air temperatures of 16, 24, and 32 C from a desktop ventilation
Experimental study of the thermal behavior of direct absorption parabolic trough collector by applying copper metal foam as volumetric solar absorption
M Valizade, MM Heyhat, M Maerefat
Journal PapersRenewable Energy , Volume 145 , 2020 January 1, {Pages 261-269 }
Abstract
The effects of using copper metal foam as a volumetric absorber as well as heat transfer enhancement technique on the thermal characteristics of a direct absorption parabolic trough solar collector are examined experimentally. The thermal performance, temperature difference and friction factor for PTC in three cases (full porous, semi-porous and without porous) are investigated and compared with each other. The experiments were performed in different flow rates and inlet temperatures. The thermal performance of solar collector is calculated based on ASHRAE Standard 93-2010. Obtained results indicate that using porous foam increase the friction factor dramatically. Moreover, the maximum temperature differences for full-porous, semi-porous an
In the present work, the effects of using nanofluid, metal foam and their combination on the thermal performance of direct absorption parabolic trough solar collector (DAPTSC) were examined experimentally. The use of these volumetric absorbers were introduced because of some of their characteristics such as superior optical properties and better flow mixing which can lead to a lower thermal losses. In order to compare the optical properties of nanofluids and metal foam, the spectrometric experiments were also performed. Obtained results confirm that both nanofluid and metal foam are good solar absorbers. Therefore, CuO/water nanofluids at different volume concentrations (0.01%, 0.05%, and 0.1%) were examined as volumetric solar absorbers. O
Intelligent models to predict the indoor thermal sensation and thermal demand in steady state based on occupants’ skin temperature
Behrouz Salehi, Abdul Hamid Ghanbaran, Mehdi Maerefat
Journal PapersBuilding and Environment , Volume 169 , 2020 February 1, {Pages 106579 }
Abstract
The correct prediction of thermal sensation is an important factor in energy consumption and satisfaction of occupants. This study examined the effectiveness of six different intelligent approaches for predicting thermal sensation and demand using body temperature data of 615 experiments with an exposure time of 3?h in a controlled office place. At each hour, the temperature of 14 uncovered body points was measured and finally, 1845 temperature data points were extracted. The exposure time had a significant effect on the thermal sensation and insufficient impact on the body temperature. Among all measured temperature data points, four points including middle of forehead (MFH), left cheek (LC), Nose (No), and left hand (LH), were taken as mo
Journal PapersJournal of Thermal Analysis and Calorimetry , 2020 January 11, {Pages 11-Jan }
Abstract
This study evaluates the cooling performance of a new hybrid system composing of an earth-to-air heat exchanger (EAHE) and a water spray channel to provide thermal comfort in Tehran, Iran. The inlet air temperature passing through the EAHE dissipates its heat to the surrounding soil and become slightly colder. To reach thermal comfort, the pre-cooled air flows upward through a channel spraying water downward and enters the living space. Considering the evaporative thermal comfort zone, the results showed that this system can meet comfort conditions for summer season Tehran. Moreover, according to the results, the cooling effectiveness of the proposed hybrid system is more than 100%, which means that the integrated system is capable of decr
Effect of Swirl on Thermal and Hydraulic Properties of Ice Slurry Flow
Hazhir Ahmadkermaj, Reza Maddahian, Mehdi Maerefat
Journal PapersHeat Transfer Engineering , 2020 March 6, {Pages 23-Jan }
Abstract
Accumulation of ice particles inside the pipes of an ice slurry refrigeration system is a problem that should be avoided to ensure the efficient performance of the system. In the present research, the swirling flow of ice slurry is numerically investigated using the Eulerian-Eulerian model coupled with the kinetic theory of granular flow. The swirling flow is generated by twisted tapes inserted into a smooth pipe. The results show that by swirling the flow, the ice particle diameter may be increased up to about three times larger than the typical particle diameter used in the ice slurry, without particle accumulation. Moreover, for the swirling flow of ice slurry with the ice particle diameter of 0.3 mm, the rate of mass transfer increase
Analytical solution for heat transfer problem in a cross-flow plate heat exchanger
Mehdi Seddiq, Mehdi Maerefat
Journal PapersInternational Journal of Heat and Mass Transfer , Volume 163 , 2020 December 1, {Pages 120410 }
Abstract
Cross-flow plate heat exchangers are used for plenty of applications in industrial and domestic sectors, and the analysis of heat transfer is a key for the evaluation of their performance. There are challenges for an analytical study because heat transfer in each channel is governed by a partial differential equation coupled with temperature fields in the adjacent channels representing a three-dimensional problem. The problem is even more complicated in the turbulent regime as the effective thermal diffusivity varies within the channel cross-section. In the present study, a separate set of governing equations and boundary conditions are considered for each part of the heat exchanger. Appropriate profiles for the flow velocity and thermal di
Experimental investigation of the effect of personalized ventilation system on distribution of temperature, velocity and draught discomfort in an office environment
Alireza Zolfaghari, Peyman Ebrahimi Naghani, Mehdi Maerefat
Journal PapersAmirkabir Journal of Mechanical Engineering , 2020 November 2, {Pages }
Abstract
In this research, it has been tried to experimentally investigate the the effect of personalized ventilation system on air flow and temperature distribution in a room for two inlet air temperatures (24 and 32?C) and two different arrangements of the inlet diffusers (desk-mounted and under-desk air terminals). The results showed that the penetration depth of heat and momentum due to the inlet diffuseres were not the same; So that the effect of inlet diffusers’ temperature on the room temperature distribution is significant up to a distance of about 60 cm. However, the effect of inlet velocity is noticeable up to a distance of about 110 cm. As a result, the occupants’ thermal sensations up to about one meter from the inlet diffusers will
Experimental comparison of optical properties of nanofluid and metal foam for using in direct absorption solar collectors
M Valizade, MM Heyhat, M Maerefat
Journal PapersSolar Energy Materials and Solar Cells , Volume 195 , 2019 June 15, {Pages 71-80 }
Abstract
Open-cell porous metal foams and nanofluids are among the solar absorbers for radiation absorption in solar collectors. The optical properties of absorbers have an important role in the thermal performance of direct and volumetric absorption solar collectors. In the present work, porous foam and nanofluid are made from the same materials and their optical properties are measured experimentally. The spectrophotometric experiments are performed on the produced porous metal foams and water based nanofluids from two materials namely SiC and CuO. In water-saturated porous foams, the effect of porosity (90% and 95%), pore diameter (10PPI-30PPI) and type of material (CuO and SiC) are survived while the influence of volume fraction and kind of nano
Assessment of overall body thermal sensation based on the thermal response of local cutaneous thermoreceptors
Negin Moallemi Khiavi, Mehdi Maerefat, Seyed Alireza Zolfaghari
Journal PapersJournal of Thermal Biology , 2019 May 31, {Pages }
Abstract
In non-uniform environments, different body parts may experience different ranges of physical/environmental parameters. Therefore, to assess the overall thermal sensation in non-uniform environments, the local temperature/thermal sensation of various body parts should be calculated. The local temperature/thermal sensation based on cutaneous thermoreceptor (TRs) responses has been evaluated using MSTB (Multi-Segmental Thermoregulatory Bioheat) model and LTRESP (Local Thermal Response) index in our recent studies. In the present study, a new combined method was proposed to evaluate the overall thermal sensation considering the effects of local sensations of various body segments. In this new method, the local sensations predicted by LTRESP in
Role of Vessel Microstructure in the Longevity of End-to-side Grafts
Mehdi Ramezanpour, Farhad Rikhtegar Nezami, Nahid Ramezanpour, Foad Kabinejadian, Mehdi Maerefat, Gerhard A Holzapfel, Joseph Bull
Journal PapersJournal of biomechanical engineering , 2019 May 29, {Pages }
Abstract
Compliance mismatch between the graft and the host artery of an end-to-side (ETS) arterial bypass graft anastomosis increases the intramural stress in the ETS graft-artery junction, and thus may compromise its long-term patency. The present study takes into account the effects of collagen fibers to demonstrate how their orientations alter the stresses. The stresses in a ETS bypass graft anastomosis, as a man-made bifurcation, are compared to those of its natural counterpart with different fiber orientations. Both of the ETS bypass graft anastomosis and its natural counterpart have identical geometric and material models and only their collagen fiber orientations are different. The results indicate that the fiber orientation mismatch between
NUMERICAL INVESTIGATION OF THE EFFECTS OF BED SHAPE ON THE END-TO-SIDE CABG HEMODYNAMICS
MEHDI RAMEZANPOUR, MEHDI MAEREFAT, NAHID RAMEZANPOUR, MANIJHE MOKHTARI-DIZAJI, FARIDEH ROSHANALI, FARHAD RIKHTEGAR NEZAMI
Journal PapersJournal of Mechanics in Medicine and Biology , 2019 May 17, {Pages 1950019 }
Abstract
Disrupted flow initiates and aggravates intimal thickening in the end-to-side (ETS) coronary artery bypass grafting (CABG), which may lead to failure. To enhance the post-intervention hemodynamics, the geometry is either optimized or totally reconfigured. Majority of configurations proposed by researchers have not suited CABG surgery, for they entailed rigorous manipulation on conventional grafts in situ, which was neither swift nor straightforward. The aim of the present study is, thus, to introduce a slight, yet effective, modification to a conventional ETS CABG configuration, and numerically investigate its effects on updated hemodynamic and structural environment, anticipating the longevity of proposed configuration and CABG success. Th
An innovative PCM system for thermal comfort improvement and energy demand reduction in building under different climate conditions
Mohamad Ahangari, Mehdi Maerefat
Journal PapersSustainable Cities and Society , Volume 44 , 2019 January 1, {Pages 120-129 }
Abstract
In recent years, applying phase change materials (PCMs) has attracted growing attention due to its potential to energy conservation with thermal comfort in the buildings. The proper use of PCM in a building can reduce the energy demand considerably, keeping the indoor temperature within the comfort range. One of the major issues associated with the use of PCM is the dependency of its performance on the climate conditions, such as the ambient temperature in which it is used. This study introduces an innovative double layer PCM system aim to improve thermal comfort conditions and minimize energy demand. In the scope of PCM performance improvement under different climates during hot and cold months, a constructive solution is the incorporation
Mendelian susceptibility to mycobacterial disease: Clinical and immunological findings of patients suspected for IL12Rβ1 deficiency.
M Ramezanpour, N Ramezanpour, F Kabinejadian, M Maerefat, GA Holzapfel, J Bull
Journal Papers , 2019 January , {Pages }
Abstract
Compliance mismatch between the graft and the host artery of an end-to-side (ETS) arterial bypass graft increases the intramural stress in the ETS graft-artery junction, and thus may compromise its long-term patency. The present study takes into account the effects of collagen fibers to demonstrate how their orientations alter the stresses. The stresses in a bypass graft, as a man-made bifurcation, are compared to those of its natural counterparts with different fiber orientations. The results indicate that the fiber orientation mismatch between the graft and the host artery may increase the stresses at both the heel and toe regions of the ETS anastomosis (the maximum principal stress at the heel and toe regions increased by 72 and 12%, res
The optimal insulation thickness is a function of the insulation initial cost and the cost of energy carriers for the internal space heating and cooling due to heat transfer from the wall. In Iran, by allocating subsidies to the energy sector, tariffs for energy carriers are sensibly lower than global prices. In order to determine the insulation optimal thickness, energy carrier tariffs were considered variable according to consumption. Electricity and gas costs were divided into 4 ascending tariffs for low, moderate, high, and very high consumption cases. In addition, the case of energy carriers without subsidies was also examined the 5. The outer wall consists of a typical hollow with 20cm thickness, insulated with an expanded polystyrene
The enhancement of pollutant removal in underground enclosed parking lots by reconsideration of the exhaust vent heights
Javad Aminian, Mehdi Maerefat, Ghassem Heidarinejad
Journal PapersTunnelling and Underground Space Technology , Volume 77 , 2018 July 1, {Pages 305-313 }
Abstract
Increasing indoor air quality (IAQ) is the main aim of employing ventilation systems in enclosed parking lots. The proper placement of supply air inlets and exhaust vents have great contribution in increasing indoor air quality and reduces both the amount of contaminant and energy consumption in parking lots. In this paper, the numerical simulation has been performed to assess effects of these parameters. The conservation equations with appropriate boundary conditions have been solved. The effect of exhaust vent locations on increasing IAQ has been investigated and its effect on flow pattern and energy consumption has been found. The results indicate that, if there is a longitudinal ventilation flow in the parking lot and the exhaust vents
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اسحق بيك فرد, فراز
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راعي, عليرضا
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مسعودي راد, حسن
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منيعي, سياوش
مدلسازي يك سامانه هيبريدي فتوولتائيك حرارتي و مبدل گرمايي زمين-هوا در گلخانه هاي تجاري كشور