scholarly journals Effects of PCM thermal properties and thermodiode panel (TDP) on buildings' energy demand and indoor temperature

2021 ◽  
Author(s):  
Mohammad Ebrahim Poulad
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Thermal Properties ◽  
Air Temperature ◽  
Indoor Air ◽  
Energy Demand ◽  
Temperature Fluctuations ◽  
Solar Thermal Energy ◽  
Indoor Temperature ◽  
Aluminium Sheets

The performance of a thermodiode panel (TDP) is investigated thoroughly. A phase change material (PCM) layer is integrated into the TDP. A TDP can transfer solar thermal energy into the building. Adding a PCM layer to the TDP adds capacity of storing solar energy into the TDP, and releases the stored energy when the sun goes down. The TDP is composed of dense foam, which is sandwiched between two aluminium sheets, and a thermosyphon passes through the foam layer. PCM layer is added to the condenser section of the TDP that is connected into the building envelope. PCM thermal properties and their effects on energy demand and indoor temperature are investigated on a typical building. The best melting point for the PCM was found to be a temperature in the middle of the set points (upper and lower). Quantitative indices are introduced to evaluate the effects of PCM on indoor air temperature fluctuations. PCM reduces the indoor air temperature fluctuations. Increasing thermal conductivity of PCM by an order of magnitude reduces about 2% annual energy demand of a building. Regarding convention heat transfer coefficient, by increasing the convective heat transfer coefficient at interior wall surface, the cooling demand slightly increases in summer. In winter, energy demand is sensitive to h-value with a positive correlation. Matlab codes developed using genetic algorithm to optimize the TDP sizes, i.e., thicknesses of three aluminium sheets, copper tube diameter and its thickness that makes the structure of thermosyphon. The optimum sizes found to be: plate thicknesses of 1.5 mm, 2.5 mm, and 2 mm and thermosyphon diameter and thickness of 32 mm and 9 mm, respectively, provide the maximum objective function (the best performance of the TDP). Thermal bridging of a TDP can be reduced 76 times by adding a piece of Teflon in the thermosyphon assembly. The integration can do both store and collect/gain solar thermal energy, which makes this panel a novel alternative for south walls. It is also shown that thermosyphon angle from the horizon shall be between 30 and 45 degree to have the best performance of the TDP.

scholarly journals Effects of PCM thermal properties and thermodiode panel (TDP) on buildings' energy demand and indoor temperature

2021 ◽  
Author(s):  
Mohammad Ebrahim Poulad
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Thermal Properties ◽  
Air Temperature ◽  
Indoor Air ◽  
Energy Demand ◽  
Temperature Fluctuations ◽  
Solar Thermal Energy ◽  
Indoor Temperature ◽  
Aluminium Sheets

The performance of a thermodiode panel (TDP) is investigated thoroughly. A phase change material (PCM) layer is integrated into the TDP. A TDP can transfer solar thermal energy into the building. Adding a PCM layer to the TDP adds capacity of storing solar energy into the TDP, and releases the stored energy when the sun goes down. The TDP is composed of dense foam, which is sandwiched between two aluminium sheets, and a thermosyphon passes through the foam layer. PCM layer is added to the condenser section of the TDP that is connected into the building envelope. PCM thermal properties and their effects on energy demand and indoor temperature are investigated on a typical building. The best melting point for the PCM was found to be a temperature in the middle of the set points (upper and lower). Quantitative indices are introduced to evaluate the effects of PCM on indoor air temperature fluctuations. PCM reduces the indoor air temperature fluctuations. Increasing thermal conductivity of PCM by an order of magnitude reduces about 2% annual energy demand of a building. Regarding convention heat transfer coefficient, by increasing the convective heat transfer coefficient at interior wall surface, the cooling demand slightly increases in summer. In winter, energy demand is sensitive to h-value with a positive correlation. Matlab codes developed using genetic algorithm to optimize the TDP sizes, i.e., thicknesses of three aluminium sheets, copper tube diameter and its thickness that makes the structure of thermosyphon. The optimum sizes found to be: plate thicknesses of 1.5 mm, 2.5 mm, and 2 mm and thermosyphon diameter and thickness of 32 mm and 9 mm, respectively, provide the maximum objective function (the best performance of the TDP). Thermal bridging of a TDP can be reduced 76 times by adding a piece of Teflon in the thermosyphon assembly. The integration can do both store and collect/gain solar thermal energy, which makes this panel a novel alternative for south walls. It is also shown that thermosyphon angle from the horizon shall be between 30 and 45 degree to have the best performance of the TDP.

scholarly journals Thermal history and comfort in a Brazilian subtropical climate: a 'cool' addiction hypothesis

2016 ◽  
Vol 16 (1) ◽  
pp. 7-20 ◽  
Author(s):  
Renata De Vecchi ◽  
Christhina Maria Cândido ◽  
Roberto Lamberts
Keyword(s):  
Air Temperature ◽  
Indoor Air ◽  
Thermal History ◽  
Air Conditioning ◽  
Prolonged Exposure ◽  
Temperature Fluctuations ◽  
Subtropical Climate ◽  
Indoor Thermal Comfort ◽  
Air Speed ◽  
The Impact

Abstract Currently, there is a rising trend for commercial buildings to use air conditioning to provide indoor thermal comfort. This paper focuses on the impact of prolonged exposure to indoor air-conditioned environments on occupants' thermal acceptability and preferences in a mixed-mode building in Brazil. Questionnaires were administered while indoor microclimatic measurements were carried out (i.e., air temperature, radiant air temperature, air speed and humidity). Results suggest significant differences in occupants' thermal acceptability and cooling preferences based on thermal history; differences were found between groups based on different physical characteristics (i.e., different gender and body condition). The findings also indicated a significant potential to implement temperature fluctuations indoors when occupants are exposed to air conditioning environments in warm and humid climates.

scholarly journals THE INFLUENCE OF THE CHANGES IN WIND VELOCITY ON THE OUTER HEAT EXCHANGE OF THE BUILDINGS

2021 ◽  
pp. 148-155
Author(s):  
D.V. Tarasevych ◽  
◽  
O.V. Bogdan ◽  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchange ◽  
Transfer Coefficient ◽  
Heat Loss ◽  
Wind Velocity ◽  
Air Temperature ◽  
Outer Surface ◽  
Climatic Parameters ◽  
The Heat Transfer Coefficient

When choosing architectural and planning solutions, such climatic factors as air temperature and humidity, having scalar quantities, as well as solar radiation, wind and precipitation having vector characteristics, must be taken into account. The calculated climatic parameters for the design of building enclosing structures, heat loss calculations and heat supply regulation are provided in the current documentation on norms and standards. The practical exploitation of various buildings demonstrates that in terms of initial climatic data, the choice of design parameters is not always efficiently justified; hence, the influence of the environment on the heating regime of the structures is insufficient in the estimations and sometimes erroneous. The wind is one of such climatic parameters. Its velocity and repeatability impact the heat exchange of the building structure with the environment as well as the alteration in temperature regime. The wind current towards the building creates additional pressure on the facade of the construction from the wind side direction. This leads, firstly, to air infiltration via the enclosing structures, and secondly, to the rise of heat exchange from the outer surface of the wall on the windward side. Based on estimated and analytical research, the values of the change in wind velocity depending on the altitude were analyzed, and its influence on the heat loss during heating of multi-storey buildings was assessed. The alterations in the wind velocity depending on the altitude were analyzed in the conditions of dense (urban) and broad construction. Besides, the authors presented the dependence of the convective component of the heat transfer coefficient of the outer surface of the structure on the values of the wind velocity. Based on the performed and presented calculations, it can be noticed that the heat transfer of the external structure will be much higher for multi-storey buildings than for mid-rise constructions. Thus, the convective component of the heat transfer coefficient of the outer surface rises by 36 % when the wind velocity increases from 5 m/s to 7 m/s. If not taking into consideration this dependence in the design, it can significantly influence the estimation of heat loss and energy efficiency of buildings, especially when it is about the increased percentage of facades glazing. The authors of the article assessed the heat loss for heating the windward and leeward facades at average values of the outside air temperature during the heating season in Ukraine. Hence, for constructions higher than 70 m with a calculated wind velocity of 5 m/s, heat losses increase from 10 % to 19 %. Such great difference in heat loss between the windward and leeward walls of the building requires increased thermal protection from the prevailing winter winds. Therefore, when designing multi-storey buildings, it is necessary to take into account changes in wind velocity according to the altitude. The obtained results can be useful both for choosing architectural and planning solutions, like the materials for external enclosing structures and for the objective assessment of the wind protection degree of individual buildings and territories.

scholarly journals Air Distribution and Air Handling Unit Configuration Effects on Energy Performance in an Air-Heated Ice Rink Arena

Energies ◽  
2019 ◽  
Vol 12 (4) ◽  
pp. 693 ◽  
Author(s):  
Mehdi Taebnia ◽  
Sander Toomla ◽  
Lauri Leppä ◽  
Jarek Kurnitski
Keyword(s):  
Temperature Gradient ◽  
Air Temperature ◽  
Indoor Air ◽  
Energy Demand ◽  
Energy Performance ◽  
Air Distribution ◽  
Air Handling Unit ◽  
Cooling Coil ◽  
Indoor Conditions ◽  
Cooling Energy Demand

Indoor ice rink arenas are among the foremost consumers of energy within building sector due to their exclusive indoor conditions. A single ice rink arena may consume energy of up to 3500 MWh annually, indicating the potential for energy saving. The cooling effect of the ice pad, which is the main source for heat loss, causes a vertical indoor air temperature gradient. The objective of the present study is twofold: (i) to study vertical temperature stratification of indoor air, and how it impacts on heat load toward the ice pad; (ii) to investigate the energy performance of air handling units (AHU), as well as the effects of various AHU layouts on ice rinks’ energy consumption. To this end, six AHU configurations with different air-distribution solutions are presented, based on existing arenas in Finland. The results of the study verify that cooling energy demand can significantly be reduced by 38 percent if indoor temperature gradient approaches 1 °C/m. This is implemented through air distribution solutions. Moreover, the cooling energy demand for dehumidification is decreased to 59.5 percent through precisely planning the AHU layout, particularly at the cooling coil and heat recovery sections. The study reveals that a more customized air distribution results in less stratified indoor air temperature.

scholarly journals An Online Grey-Box Model Based on Unscented Kalman Filter to Predict Temperature Profiles in Smart Buildings

Energies ◽  
2020 ◽  
Vol 13 (8) ◽  
pp. 2097 ◽  
Author(s):  
Marco Massano ◽  
Edoardo Patti ◽  
Enrico Macii ◽  
Andrea Acquaviva ◽  
Lorenzo Bottaccioli
Keyword(s):  
Kalman Filter ◽  
Internet Of Things ◽  
Air Temperature ◽  
Indoor Air ◽  
Unscented Kalman Filter ◽  
Box Model ◽  
Indoor Temperature ◽  
Thermal Dynamics ◽  
Thermal Network ◽  
Realistic Data

Nearly 40% of primary energy consumption is related to the usage of energy in Buildings. Energy-related data such as indoor air temperature and power consumption of heating/cooling systems can be now collected due to the widespread diffusion of Internet-of-Things devices. Such energy data can be used (i) to train data-driven models than learn the thermal properties of buildings and (ii) to predict indoor temperature evolution. In this paper, we present a Grey-box model to estimate thermal dynamics in buildings based on Unscented Kalman Filter and thermal network representation. The proposed methodology has been applied in two different buildings with two different thermal network discretizations to test its accuracy in indoor air temperature prediction. Due to a lack of a real-world data sampled by Internet of Things (IoT) devices, a realistic data-set has been generated using the software Energy+, by referring to real industrial building models. Results on synthetic and realistic data show the accuracy of the proposed methodology in predicting indoor temperature trends up to the next 24 h with a maximum error lower than 2 °C, considering one year of data with different weather conditions.

Evaluation of Heating Process of Apple, Eggplant, Zucchini and Potato by Means of Their Thermal Properties

2016 ◽  
Author(s):  
Hilario Terres ◽  
Sandra Chavez ◽  
Raymundo Lopez ◽  
Arturo Lizardi ◽  
Araceli Lara
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Thermal Properties ◽  
Transfer Coefficient ◽  
Biot Number ◽  
Heating Process ◽  
Energy Devices ◽  
Heating Device ◽  
The Heat Transfer Coefficient ◽  
Transitory State

In this work, the heating process for apple, eggplant, zucchini and potato by means of evaluation of their thermal properties and the Biot number determined in experimental form is presented. The heating process is carried out using a solar cooker box-type as heating device. The thermal experimental properties determined are conductivity (k), density (D), specific heat (C), diffusivity (Dif) and the Biot number (Bi) for each product evaluated. In the experimentation, temperatures for center and surface in each product and water were measured in controlled conditions. For those measures, a device Compact Fieldpoint and thermocouples placed in the points studied were used. By using correlations with temperature as function, k, D and C were calculated, while by using equations in transitory state for the products modeled as sphere and cylinder was possible to estimate the Biot number after calculation of the heat transfer coefficient for each case. Results indicate the higher value for k, C and Dif correspond to zucchini (0.65 W/m °C, 4084.5 J/kg °C, 1.5 × 10−7 m2), while higher value for D correspond to potato (1197.5 kg/m3). The lowest values for k and C were obtained for potato (0.59 W/m °C, 3658.3 J/kg °C) while lowest values for D and Dif, correspond to zucchini (998.2 kg/m3) and potato (1.45 × 10−7 m2/s) respectively. The maximum and minimum values for Bi corresponded to potato (21.4) and zucchini (0.41) in respective way. The results obtained are very useful in applications for solar energy devices, where estimates for properties are very important to generate new results, for example, numerical simulations. Also, results could be used to evaluate the cooking power in solar cookers when the study object is oriented in that direction.

scholarly journals ENHANCING HEAT TRANSFER COEFFICIENT AND BREAKDOWN STRENGTH OF MINERAL OIL BY (AL2O3 AND TIO2) NANOPARTICLES

2021 ◽  
Vol 25 (Special) ◽  
pp. 2-33-2-38
Author(s):  
Mohammad M. Ali ◽  
◽  
Amer H. Majeed ◽  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Thermal Properties ◽  
Transfer Coefficient ◽  
Breakdown Strength ◽  
Dielectric Strength ◽  
Mineral Oil ◽  
Nano Particles ◽  
Paper Study ◽  
Enhancing Heat Transfer

The aims of this paper study the effects of two types of nanoparticle on dielectric strength and heat transfer coefficient within mineral oil used in an electrical transformer. These nanoparticles (NPs) including (semi conductive TiO2 and insulating Al2O3), have been prepared with the same size and surface modification, it is shown that nano-particles enhance insulating and thermal properties of mineral oil as well as the degree of enhancement is dependent on the NPs concentration.

scholarly journals Comparison of Optimized and Conventional Models of Passive Solar Greenhouse—Case Study: The Indoor Air Temperature, Irradiation, and Energy Demand

Energies ◽  
2021 ◽  
Vol 14 (17) ◽  
pp. 5369
Author(s):  
Saleh Mohammadi ◽  
Esmail Khalife ◽  
Mohammad Kaveh ◽  
Amir Hosein Afkari Sayyah ◽  
Ali Mohammad Nikbakht ◽  
...  
Keyword(s):  
Air Temperature ◽  
Indoor Air ◽  
Energy Demand ◽  
Lightweight Concrete ◽  
Concrete Block ◽  
Coefficient Of Determination ◽  
Solar Greenhouse ◽  
Temperature Irradiation ◽  
Optimized Model ◽  
Passive Solar

This study was carried out to optimize a computational model of a new underground passive solar greenhouse to improve thermal performance, storage, and saving of heat solar energy. Optimized and conventional passive solar greenhouse were compared in regards of indoor air temperature, irradiation, and energy demand. Six different materials were used in the conventional model. In addition, TRNSYS software was employed to determine heat demand and irradiation in the greenhouse. The results showed that the annual total heating requirement in the optimized model was 30% lower than a conventional passive solar system. In addition, the resulting average air temperature in the optimized model ranged from −4 to 33.1 °C in the four days of cloud, snow, and sun. The average air temperature in the conventional passive solar greenhouse ranged from −8.4 to 24.7 °C. The maximum monthly heating requirement was 796 MJ/m2 for the Wtype87 model (100-mm lightweight concrete block) and the minimum value was 190 MJ/m2 for the Wtype45 model (50-mm insulation with 200-mm clay tile) in a conventional passive solar greenhouse while the monthly heating requirement estimated 126 MJ/m2 for the optimized greenhouse model. The predictability of the TRNSYS model was calculated with a coefficient of determination (R2) of 95.95%.

scholarly journals Study on the Thermal Properties of Hollow Shale Blocks as Self-Insulating Wall Materials

2017 ◽  
Vol 2017 ◽  
pp. 1-12 ◽  
Author(s):  
Guo-liang Bai ◽  
Ning-jun Du ◽  
Ya-zhou Xu ◽  
Chao-gang Qin
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Thermal Properties ◽  
Transfer Coefficient ◽  
Wall Material ◽  
Element Analysis ◽  
Experimental Heat ◽  
Wall Materials ◽  
Save Energy ◽  
The Heat Transfer Coefficient

To reduce energy consumption and protect the environment, a type of hollow shale block with 29 rows of holes was designed and produced. This paper investigated the thermal properties of hollow shale blocks and walls. First, the guarding heat-box method was used to obtain the heat transfer coefficient of the hollow shale block walls. The experimental heat transfer coefficient is 0.726 W/m2·K, which would save energy compared to traditional wall materials. Then, the theoretical value of the heat transfer coefficient was calculated to be 0.546 W/m2·K. Furthermore, the one-dimensional steady heat conduction process for the block and walls was simulated using the finite element analysis software ANSYS. The predicted heat transfer coefficient for the walls was 0.671 W/m2·K, which was in good agreement with the test results. With the outstanding self-insulation properties, this type of hollow shale block could be used as a wall material without any additional insulation measures in masonry structures.

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