Thermal Energy Conservation Research Articles

A Numerical Study of Fluid Flow and Heat Transfer in Carbon Dioxide Enclosures on Mars

In order to support the future thermal control and energy conservation design for the Mars rover, numerical studies on natural convection in CO2 enclosures on Mars’ surface were conducted for both horizontal and vertical enclosures. The parameters are as follows: the atmospheric pressure was 1000 Pa, the gravitational acceleration was 3.62 m/s2, and the Prandtl number was 0.77. The heat flux, temperature, and velocity fields of the CO2 enclosures were obtained with the aspect ratio ranging from 5.56 to 200 and the Grashof number ranging from 430 to 2.6 × 104. It was found that natural convection formed more easily in the horizontal enclosures than that in the vertical enclosures when the enclosures had same thickness. With the increasing thickness of the enclosures, Rayleigh–Bénard convections formed in the horizontal enclosures, while only single-cell convections formed in the vertical enclosures. The heat flux through the horizontal enclosures was greater than that through the vertical enclosures with the same thickness when natural convection formed. The maximum difference between them reached 35.26%, which was illustrated by the field synergy principle. A hysteresis phenomenon of the natural convection dominating the heat transfer was found in the vertical enclosure on Mars’ surface. New values for the critical Grashof number and correlations for the average Nusselt number for both the horizontal and vertical CO2 enclosures on Mars’ surface were also developed.

The Interpretation and Inheritance of Green Local Building Material System in Modern Architecture - Case Study of Century Fishing Village Eelgrass Cottage Resort in Dayu Island, Shidao Bay, Jiaodong Peninsula

Dayu island sea cottage is the most typical carrier of the fish culture in the coastal area of Jiaodong. In recent years, economic development, changes in fishermen's living habits led to a the dismantling of a large number of traditional sea cottages and gradual disappearing of unique Dayu island building materials system comprising of eelgrass roof, local granite stone wall and soil kang chimney. In order to protect the local cultural characteristics so they can be passed down, the paper sorted out the original traditional eelgrass cottage building material system. The project of Century Fishing Village Eelgrass Cottage Resort represents experimentation and innovation on the original material system, forming a novel construction material system. Such a system not only satisfies the requirement of new buildings on thermal insulation, energy and space conservation, but also enhances safety and resistance to wind, erosion. The wide adoption of the new material system in new buildings enhances the technique of integrating traditional construction materials and modern architecture in both form and function, making it an ideal design strategy.

Three-dimensional transient numerical model for the thermal performance of the solar receiver

Abstract For solar thermal power plants, no steady-state operation occurs in view of inherently transient natures of their initial and boundary conditions. So this study proposes a mathematical model to perform the analysis on the transient behaviors of the external solar receiver in the tower power technology. This 3D transient model was established by dividing the receiver tube into discrete control volumes and then applying the conservation of thermal energy to every single differential control volume. In addition, this model was validated by simulating the HTF temperature distributions and then comparing them with the reference results. By calculating the time-dependent and non-uniform temperature fields of the receiver tube, this paper focuses attention on the evolution of transient processes in several common scenarios involving the mass flowrate variation, the start-up process and the occurrence of the heavy clouds above the heliostat field. Particularly, the analysis of the transient thermal performance highlights some noteworthy characteristics including serious problems such as the corrosion, the thermal stress and the fatigue in the typical transitions, which might require the control system to correspondingly adjust in time.

Case study of an advanced integrated comfort control algorithm with cooling, ventilation, and humidification systems based on occupancy status

In this study, we propose a new control algorithm based on occupancy status for indoor environmental devices to maintain thermal comfort while saving energy of residential buildings. The algorithm consists of two parts: an environmental data driven model for the occupancy status detection and an integrated comfort algorithm for operating the indoor devices. To detect the occupancy status, a multinomial logistic regression model is developed based on the data obtained from passive infrared (PIR) sensors, a door sensor, CO2 concentrations, and lighting electricity consumption. The occupancy status is categorized into three classes: away, active, and inactive (sleep).The new control algorithm integrates and operates air-conditioning, ventilation, and humidification systems by considering the outdoor environment, and ensuring indoor thermal comfort and energy savings at each occupancy status. The control algorithm is evaluated at different outdoor conditions with a testbed that consists of a variable refrigerant flow (VRF) air conditioning system, humidifier, and ventilation system.The performance of the proposed control algorithm is experimentally compared with that of a conventional individual control method in terms of the thermal comfort and energy consumption. The results show that the advanced integrated comfort control system improves the thermal comfort and decreases the energy consumption. Specifically, Case 1 (active, hot, and mild humidity) exhibits a 6.3% energy reduction and 64% improvement in the thermal comfort. Case 2 (active, hot, and low humidity) shows a 21% energy reduction and 72% improvement in the thermal comfort. Case 3 (inactive, comfort indoors) displays a 7% energy increase and 31% improvement in the thermal comfort. These results confirm that the proposed advanced integrated comfort control algorithm could be useful for designing better space environmental control to ensure thermal comfort and energy conservation.

Microencapsulation of Butyl Stearate as Phase Change Material by Melamine Formaldehyde Shell for Thermal Energy Storage

Butyl stearate as a phase change material was microencapsulated within melamine-formaldehyde resin using emulsion polymerization. Morphology and thermal specification of produced microcapsules were studied by Fourier transform infrared spectroscopy, FT-IR, scanning electron microscopy, SEM, and Differential scanning calorimetry analysis, DSC. FT-IR spectra validated the existence of the butyl stearate in the core of microcapsules. SEM graphs showed that melamine formaldehyde polymer without core was spherical and almost uniform with an approximate size of 2µm and microcapsules of butyl stearate in melamine formaldehyde shell were also spherical with the average diameter of 4µm. DSC results showed that microencapsulation reduced the latent heat of melting and freezing of butyl stearate and increased melting point. The performance of the produced microcapsules was obtained 36.64%. Moreover, the efficiency of energy storage by the microcapsules was obtained about 40%. It was observed that the rate of thermal energy conservation was high during the phase change process of microcapsule core and it was reduces after completion of the melting process.

Laser-driven calorimetry measurements of petroleum and biodiesel fuels

Thermochemical characteristics were determined for several National Institute of Standards and Technology standard-reference-material petroleum and biodiesel fuels, using a novel laser-heating calorimetry technique. Measurements focused on the sample thermal behavior, specific heat release rate, and total specific heat release. The experimental apparatus consists of a copper sphere-shaped reactor mounted within a chamber, along with laser-beam-steering optical components, gas-supply manifold, and a computer-controlled data-acquisition system. At the center of the reactor, liquid sample is injected onto a copper pan substrate that rests and is in contact with a fine-wire thermocouple. A second thermocouple is in contact with the inner reactor sphere surface. The reactor is heated from opposing sides by a continuous-wave, near-infrared laser beam to achieve nearly uniform sample temperature. The change in temperature with time (thermogram) is recorded for both thermocouples, and compared to a baseline thermogram (without liquid in the pan). The thermograms are then processed (using an equation for thermal energy conservation) for the thermochemical information of interest. The results indicated that the energy reaching the pan is dominated by radiative heat transfer processes, while the dominant thermal process for the reactor sphere is the stored (internal) thermal energy within the sphere material. Sufficient laser power is necessary to detect the fuel thermal-related characteristics, and the required power can differ from one fuel to another. With sufficient laser power, one can detect the preferential vaporization of the lighter and heavier fuel fractions. The total specific heat release obtained for the different conventional and biodiesel fuels used in this investigation were similar to the expected values available in the literature.

Two-phase natural convection dusty nanofluid flow

An analysis is performed to study the two-phase natural convection flow of nanofluid along a vertical wavy surface. The model includes equations expressing conservation of total mass, momentum and thermal energy for two-phase nanofluid. Primitive variable formulations (PVF) are used to transform the dimensionless boundary layer equations into a convenient coordinate system and the resulting equations are integrated numerically via implicit finite difference iterative scheme. The effect of controlling parameters on the dimensionless quantities such as skin friction coefficient, rate of heat transfer and rate of mass transfer is explored. It is concluded from the present analysis, that the diffusivity ratio parameter, NA and particle-density increment number, NB have pronounced influence on the reduction of heat transfer rate.

The effect of passive measures on thermal comfort and energy conservation. A case study of the hot summer and cold winter climate in the Yangtze River region

The energy consumption for heating and cooling of buildings in the cities located within the boundaries of the Hot Summer and Cold Winter (HSCW) zone in China is rapidly increasing due to the increased comfort expectations from well-resourced occupants. Guidance on how and to what extent it is possible to improve energy efficiency of buildings is thus required by policy makers as well as designers and building managers. The aim of this study is to demonstrate how the use of climate-sensitive passive design solutions can help the improvement of indoor thermal conditions while reducing the energy needs and ultimately carbon emissions. An extensive parametric analysis of several passive strategies such as building orientation, thermal insulation, glazing area, shading devices, air tightness and natural ventilation, is carried out for a typical apartment block located in the cities of Chongqing, Changsha and Shanghai, which lay respectively in the upper, middle and downstream of the Yangtze River. Detailed hourly dynamic simulations show how it is possible to extend the non-heating/cooling period and reduce the peak loads, highlighting the potentialities of each strategy according to different climate constraints. The recommended strategies provides quantitative guidance to either design of new or retrofitting of existing buildings. This research contributes to the building energy conservation knowledge for policy-makers, developers and building designers with insight on the feasibilities of the application of passive measures for residential buildings located in the Yangtze River region with hot summer and cold winter climates.

アクティブスキンを導入した高層オフィスビルにおける室内環境と省エネルギー評価 （第1報）アクティブスキンの計画概要と冬期実測結果

アクティブスキンを導入した高層オフィスビルにおける室内環境と省エネルギー評価 （第1報）アクティブスキンの計画概要と冬期実測結果

アクティブスキンを導入した高層オフィスビルにおける室内環境と省エネルギー評価 （第2報）北面におけるアクティブスキンの夏期及び冬期実測結果

アクティブスキンを導入した高層オフィスビルにおける室内環境と省エネルギー評価 （第2報）北面におけるアクティブスキンの夏期及び冬期実測結果

快適性および省エネルギー性を考慮した大学施設の性能評価 （第1報）施設概要および冬季における天井放射冷暖房の性能評価

快適性および省エネルギー性を考慮した大学施設の性能評価 （第1報）施設概要および冬季における天井放射冷暖房の性能評価

Heating chair assisted by leg-warmer: A potential way to achieve better thermal comfort and greater energy conservation in winter

Balancing thermal comfort and energy conservation has long been a hot topic in modern society. A potential way to achieve this purpose lies in extending the comfortable temperature range in buildings. This study aims to achieve better comfort and save more energy by combining heating chairs and leg-warmers. In this study, a series of experiments was conducted at the temperatures of 14, 16, 18 and 22°C, respectively. During the tests, 16 subjects (8 males and 8 females) were exposed to cool environments with different heating modes (no heating devices, heating chairs and heating chairs with leg-warmers). The obtained results showed that the combination of heating chairs and leg-warmers were superior to heating chairs. Heating chairs assisted by leg-warmers exerted greater influence on reducing cold sensation, improving comfort and acceptability (more than 80% of subjects voted on the acceptable side even at 14°C), and lowering the preference for warmth than using heating chairs alone. Also, the former one enlarged the heated area of human bodies thus achieving better local thermal sensation and comfort in cool environments. Moreover, the average heating powers of heating chairs were 34.1, 25.3 and 19.4W for each person at 14, 16 and 18°C, respectively. When assisted by leg-warmers, the average powers of heating chairs decreased to 22.6, 15.0 and 12.4W for each person at 14, 16 and 18°C, respectively, while those of leg-warmers were 18.5, 19.9 and 13.0W at 14, 16 and 18°C, respectively. As compared to the electricity consumption at 22°C without personal heating, heating chairs could save at most 61% of the total heating energy, while the combination of heating chairs and leg-warmers saved 71% due to the ability to further lower the acceptable temperature.

Indoor Climate Data Analysis Based a Monitoring Platform for Thermal Comfort Evaluation and Energy Conservation

A monitoring platform is designed, set up and used to store the measured indoor climate data such a temperature and humidity from an air-conditioned classroom to the purpose of thermal comfort evaluation. In addition, the measured current using smart current sensors at the power cables, which supply the air conditioning and ventilation system, was transmitted to the monitoring platform and calculated by soft code for the energy consumption when the air conditioner is switched on. The detail of energy and indoor climate monitoring system can be found in previous publication as well as the monitoring platform. In this paper, the data stored in the monitoring platform are used for the analysis of temperature and humidity distribution in the air conditioned room as well as the thermal comfort based on the predicted mean vote, PMV, with various occupant clothes simulated criteria. Temperature and humidity sensors are installed at various positions around the room provided 24/7 climate monitoring. In order to illustrate the thermal comfort, the comfort index is indicated by the calculation of the predicted mean vote that ranges from -3 to +3 where the zero meant neutral. The results show that the occupants wore long sleeve shirt with jacket and trouser for male, and short sleeve shirt with jacket and full-length skirt for female would reach the thermal comfort at lower temperature than others. In other words, the waste energy could be reduced simply by setting up higher cold temperature cooperated with switching off the air conditioner sometime before the end of the last class of the day, according to the indoor temperature curve analysis, which could save energy for roughly 18%.

パッシブリズミング空調における快適性と省エネルギーに関する研究 : 第1報-パッシブリズミング空調が快適性に及ぼす影響に関する実験:夏期実験結果について

パッシブリズミング空調における快適性と省エネルギーに関する研究 : 第1報-パッシブリズミング空調が快適性に及ぼす影響に関する実験:夏期実験結果について

A-28 温水床暖房の熱環境解析と省エネルギー評価 : (その1)床暖房の計算方法と精度検証

A-28 温水床暖房の熱環境解析と省エネルギー評価 : (その1)床暖房の計算方法と精度検証

A-29 温水床暖房の熱環境解析と省エネルギー評価 : (その2)人体温熱収支に基づく環境・エネルギー解析

A-29 温水床暖房の熱環境解析と省エネルギー評価 : (その2)人体温熱収支に基づく環境・エネルギー解析

Laser-Driven Calorimetry of Single-Component Liquid Hydrocarbons.

A novel laser-heating technique, referred to as the laser-driven thermal reactor (LDTR), was used to determine sample thermal (exothermic/endothermic) behavior, specific heat release rate, and total specific heat release of three volatile single-component liquid hydrocarbons, i.e., n-decane, n-butylcyclohexane and n-butylbenzene. The objective was to demonstrate measurement repeatability and extend the LDTR model from earlier investigations. The experimental apparatus consists of a copper sphere-shaped reactor mounted within a vacuum chamber, with sample and substrate supported on a thermocouple near the center of the reactor. The reactor is heated from opposing sides by a near-infrared laser to achieve nearly uniform sample temperature. The change in temperature with time (i.e., thermogram) is compared to a previously recorded baseline (no liquid sample) thermogram. A model, based on thermal energy conservation, is used to evaluate the thermograms for the thermochemical characteristics of interest. This study represents a step toward applying this technique to more complex volatile multi-component fuels of unspecified composition. Results for the LDTR were compared with a differential scanning calorimetry/thermal gravimetric analysis (DSC/TGA) instrument. The model analysis was extended to include an estimation of the hydrocarbon mass change with increasing temperature, based on the temporal change in the specific heat release rate. An estimate of the total specific heat release was obtained for these three liquid hydrocarbons and found to be consistent with the literature values when the measurements were carried out under suitable operating conditions.

Thermal environment analysis and energy conservation research of rural residence in cold regions of China based on BIM platform

In order to study the issue of rural residential energy consumption in cold regions of China, modeled an architecture prototype based on BIM platform according to the affecting factors of rural residential thermal environment, and imported the virtual model which contains building information into energy analysis tools and chose the appropriate building orientation. By analyzing the energy consumption of the residential buildings with different enclosure structure forms, we designed the optimal energy-saving residence form. There is a certain application value of this method for researching the energy consumption and energy-saving design for the rural residence in cold regions of China.

Dynamic modeling and entity validation of a photovoltaic system

We established an entitative photovoltaic (PV) module for measuring the electric power in this study. The generating electric efficiency was calculated according to the electric power. Using the heat transfer mechanism generated during the operation of PV module, thermal energy conservation law and lumped capacitance method were combined with Matlab/Simulink to establish the dynamic model of PV module. The ambient temperature, wind speed, and solar radiation of the environmental factors were the inputs used for predicting the time-varying temperature of different layers inside the module. Based on the solar cell temperature, electric power and electric efficiency could be obtained. The electric power of solar cell declined as the solar cell operating temperature increased. In this study, we used entity module to validate the accuracy of the model. The environmental factors of mounting site were applied to design the backsheet material and to improve the output performance of entity solar module. The PV dynamic model and entity validation showed that electric power and electric efficiency errors are smaller than 1.3%. The PV dynamic model can accurately predict the output performance according to the environmental factors of the site. The PV backsheet was made of glass with higher thermal conductivity to replace traditional tedlar-polyester-tedlar (TPT). Electric power and electric efficiency are increased by 2.353%. The output performance of solar module was improved effectively.

An integrated comfort control with cooling, ventilation, and humidification systems for thermal comfort and low energy consumption

Over the past few decades, interest in issues related to the global environment and energy resources have increased in many industries, including the building sector which accounts for nearly 40% of the global energy consumption. Simultaneously, the demand for precise comfort control in buildings has increased because people have acquired a better quality of life and expect more from modern technology. In most cases, air-conditioning and ventilation systems have been installed in residential and commercial buildings. However, these systems can increase energy consumption requirements because of their lack of appropriate control. Such increases can be reduced by integrating the control of available sources of cooling, humidification, ventilation, lighting, and so on. An integrated comfort control strategy that integrates an air-conditioning, a humidifier, and a ventilation system by considering the outdoor environment is proposed for ensuring indoor thermal comfort and energy savings in buildings. The control strategy was evaluated in a virtual test bed with a variable refrigerant flow system, a humidifier, and ventilation fans. The performance of the proposed integrated comfort control was compared to that of conventional individual controls using EnergyPlus in terms of thermal comfort and energy consumption. The results showed that the integrated comfort control improved thermal comfort and lowered energy consumption. The methodology of deriving the integrated comfort control was expected to be useful for designing better control logics for thermal comfort and energy conservation.