Annual variations of temperature in a sample of UK dwellings

The internal temperatures of 25 households in Northern Ireland were measured in each house at four locations: the bedrooms, living rooms, halls and kitchens, and analysed on seasonal, monthly and daily bases. In 80% of the homes the winter average daily temperature was between 15 °C and 20 °C and in summer between 20 °C and 23 °C, therefore maintaining a reasonably comfortable temperature throughout the year. In 14% of the homes, the daily average temperature was above 21 °C throughout the year, suggesting a higher household temperature than required for comfort, thus exhibiting wasteful energy behaviour. Three percent of the homes did not use their heating adequately and the winter average temperature was below 15 °C. For the majority of households, the highest indoor temperature was in August and the lowest in February. In general the peak temperatures of households occur in the evening after 8:00 pm. The peak bedroom temperatures occur between 10:00 pm and midnight and in the morning after 8:00 am. The peak living room temperature is generally in the evening while it is occupied. Correlations between the temperature difference between indoor and outdoor temperatures with outdoor temperature have been developed for each house and the four locations. The relationship between the fluctuations of average daily temperature with annual average temperature has been established.     

Performance assessment of a geothermally heated building

This study deals with an exergetic performance evaluation of a geothermally heated building. This building used in the analysis has a volume of 1147.03 m³ and a net floor area of 95.59 m², while indoor and exterior air temperatures are 20 and 0 °C, respectively. The geothermal heating system used for the heat production was constructed in the Ozkilcik heating center, Izmir, Turkey. Thermal water has a pressure of 6.8 bar, a temperature of 122 °C and a mass flow rate of 54.73 kg/s, while it is reinjected at 3.2 bar and 72 °C. The system investigated feeds three regions. Among these, the Ozkanlar region has supply/return pressure and temperature values of 4.6/3 bar and 80/60 °C, respectively. Energy and exergy flows are studied to quantify and illustrate exergy destructions in the overall system. Total exergy input rate to the system is found to be 9.92 kW and the largest exergy destruction rate occurs in the primary energy transformation at 3.85 kW.     

Induction heating with the ring effect for injection molding plates

Induction heating in injection molding has the advantages of rapid heating, reduced cycle time, and improved product quality. In this research, using both experiment and simulation, externally wrapped coil induction heating was applied to verify the heating capacity of a pair of mold plates. By applying different coil designs and mold gap, the effect of the externally wrapped coil induction heating was evaluated. Results showed that when a serial coil was used as an inductor, the heating rate reached 8.0 °C/s. From an initial mold temperature of 40 °C, after 15 s heating, the mold surface temperature reached 159.9 °C with the serial coil. The parallel coil shows a better heating uniformity but its heating rate is far lower than the serial coil. For the serial coil, the temperature distribution between the core and cavity plate are almost the same. The heating rate increases from 4.9 °C/s to 10.6 °C/s when the inductor design is changed from 5 turns to 7 turns. After 15 s heating, the temperature at point T2 increases from 40 °C to 166.7 °C and 106.1 °C with a mold gap of 1 mm, and 6 mm, respectively.     

室内低温热水地板辐射供暖系统的节能分析

本文阐述了低温热水地板辐射采暖分户热计量系统是一种易控、易调、节能的采暖系统,讨论了地板辐射供暖方式与其他方式在房间内人体热舒适方面的差异,并通过对其综合节能效果的考察,分析了地板辐射供暖系统不稳定供暖过程的数学模型,用数值计算的方法分析了间歇供暖条件下,达到室内要求温度所需的预热量与预热时间的关系。     

Gas-assisted mold temperature control for improving the quality of injection molded parts with fiber additives

A rapid heating cycle has the advantage of improving product quality in injection molding. In this study, gas-assisted mold temperature control (GMTC) was combined with cool water to achieve dynamic mold surface temperature control. By applying the GMTC system on the mold of a rectangular plate, the advantages of using GMTC for injection molding were evaluated and compared with the traditional injection molding process using different gas gap sizes and gas flow capacities. The effect of GMTC on the quality of the part was also studied. Results showed that when GMTC was used, the heating rate can reach 28 °C/s. For an initial mold temperature of 60 °C, and an air gap size of 8 mm, after 6 s heating, the mold surface temperature can reach 147.8 °C, 167.2 °C, and 229 °C with gas flow capacities of 100, 200, and 300 l/min, respectively. When the gas gap size is changed from 4 mm to 8 mm, the uniformity of temperature distribution shows a clear improvement. When GMTC was used for injection molding of parts with fiber additives, the part surface was clearly improved.     

Rapid mold temperature control in injection molding by using steam heating

The rapid heating cycle has the advantage of improving product quality in injection molding. In this study, steam heating was combined with cool water on the same mold design to achieve dynamic mold surface temperature to establish control. By applying the steam system on a TV housing mold, the advantage of using steam heating for injection molding was then evaluated and compared with water heating by experiment and simulation. The effect of steam on the quality of the part was also studied. Results showed that as steam was used, the heating time of the simple mold plate can be reduced from 18 s to 8 s with the heating rate of 9 °C/s, and the cooling time is reduced over water heating. When the target temperature is changed from 70 °C to 110 °C, the heating time of the TV housing mold plate varies from 7 s to 19 s. For the product quality, steam heating showed an improvement in both the gloss and hardness of the TV housing.     

Mold temperature control using high-frequency proximity effect induced heating

A rapid heating in an injection molding cycle has the advantage of improving product quality without significant increase in cycle time. In this study, high-frequency proximity effect induced heating (HFPEIH) was developed and combined with water cooling to achieve dynamic mold surface temperature control. By applying the HFPEIH system on a pair of mold plates separated with a small gap, the relevant influence of HFPEIH design was evaluated under various parameters including different mold plate material, inductor designs, and inductor channel depths beneath mold surface as well as mold separations. Simulation was also conducted and verified with experiments. Results show that all the heating rates range within 2 °C/s to 4 °C/s for the mold plate size of 100 mm by 100 mm. For the inductor design with three channels of circular cross section, the heating rate is fastest whereas one inductor design of rectangular shape exhibits the best the uniformity of temperature distribution. When the channel depth is reduced from 12 mm to 4 mm, the heating rate is increased significantly. The heating rate is also sensitive to mold plate surface area. When stainless steel N700 was used as the plate materials in a smaller plate of 60 mm by 60 mm, the heating rate can reach 7.6 °C/s using one channel inductor design. The mold separation exhibits that it is less sensitive to the heating rate within 1 mm to 5 mm range and when it is greater than 5 mm, the heating rate starts to decrease slightly. All the simulated results show good coincidence with experimental measurements.     

Thermoeconomic analysis method for optimization of insulation thickness for the four different climatic regions of Turkey

Thermal insulation is one of the most effective energy-conservation measures in buildings. For this reason, the energy savings can be obtained by using proper thickness of insulation in buildings. In this study, the optimum thickness of insulation considering condensed vapor in external walls are found by using exergoeconomic analysis. The four various cities from four climate zones of Turkey, namely, Antalya, ?stanbul, Elaz?? and Erzurum are selected for the analysis. The optimum insulation thickness for Antalya, ?stanbul, Elaz?? and Erzurum are obtained as 0.038, 0.046, 0.057 and 0.0739 m at indoor temperature of 20 °C, respectively. The results show that the optimum insulation thickness at the indoor temperature of 18 and 22 °C are determined as 0.0663 and 0.0816 m for the city of Erzurum, respectively. The energy saving for the city of Erzurum is found as 77.2% for the indoor temperature of 18 °C, 79.0% for the indoor temperature of 20 °C and 80.6% for the indoor temperature of 22 °C, when the optimum insulation is applied.     

Study on the heat transfer and sorption characteristics of a consolidated composite sorbent for solar-powered thermochemical cooling systems

In this paper, a new consolidated composite sorbent made from barium chloride and expanded graphite is presented for solar-powered thermochemical sorption cooling systems. A larger sorption capacity and volume cooling density can be obtained with chemisorption systems when compared with those based on physicosorption. The heat transfer and sorption characteristics of the composite sorbent were investigated. Experimental results showed that the chemical composite sorbent can effectively utilize solar energy or low-grade waste heat sources with temperature ranging from 75 to 90 °C, and it could incorporate 0.61 kg of ammonia per kg of the reactive salt. The temperature evolution in the reactor was strongly influenced by the physicochemical reaction, whereas the transient heat transfer properties in the reactive composite material were different during the decomposition and the synthesis phases owing to the variation of the ammonia content and solid configuration inside the metallic salt complex. The rate of conversion in the reactor was very sensitive to the working temperatures and pressures, and the COP (coefficient of performance) obtained with the consolidated composite sorbent varied between 0.50 and 0.53 when the evaporation temperature ranged from 0 to 15 °C at a generation temperature of 80 °C.     

Greenhouse heating and cooling using aquifer water

An aquifer coupled cavity flow heat exchanger system (ACCFHES) was designed using underground aquifer water for the heating as well as cooling of a composite climatic greenhouse. The performance of ACCFHES was experimentally evaluated for a full winter and a summer season. The ACCFHES makes use of constant temperature aquifer water (24 °C) available at an agricultural field through an irrigation tube well for heating in winter nights and cooling in summer days. The results showed that the average greenhouse room air temperature was maintained 7–9 °C above the outside air during extreme winter nights and 6–7 °C below the outside air in extreme summer days, and temperature fluctuations inside the greenhouse also decreased daily. The average relative humidity (RH) inside the greenhouse also decreased by 10–12% in the winter and increased by more than double in the extreme summer conditions as compared to the outside conditions. A comparison of economic feasibility of the ACCFHES coupled greenhouse was also conducted with conventional greenhouse and open field condition based on the yield of Capsicum annum. The ACCFHES was also compared economically with other existing heating/cooling technologies such as earth-to-air heat exchanger system (EAHES), ground air collector, evaporative cooling using foggers and fan & pad system in terms of net present worth (NPW) and pay back period. It was observed that the NPW of the ACCFHES coupled greenhouse was much higher as compared to the conventional greenhouse and open field condition. The payback period of the ACCFHES coupled greenhouse was the lowest among all other existing heating/cooling systems.     

地板辐射采暖和风机盘管采暖室内热环境及能耗比较

对地板辐射和风机盘管两种采暖方式进行了实验研究和理论分析，提出了围护结构临界热阻临的概念，推导出了两个采暖系统的热舒适性随围护结构热阻和冷风渗透量波动的变化关系。实验验证了地板辐射采暖既改善了室内热环境又显示较好的节能效果。     

Passive solar radiant system,SIRASOL. Physical–mathematical modeling and sensitivity analysis

When using passive solar heating systems, it is necessary to have available an Equator-facing facade on which to install them. Rooms without such a facade are not the best option for conventional passive solar heating systems. SIRASOL is a passive solar radiant system that captures solar energy and is to be installed in the ceiling of the room. This room must not necessarily have an Equator-facing facade. Solar energy heats up a metal sheet, which is the radiant panel, which transfers heat by long-wave radiation to the room below it. This paper presents a mathematical model and a sensitivity analysis. The mathematical model was used to analyze radiant panel temperature, radiant mean temperature, operative temperature and panel surface area. Results of the sensitivity study showed that when solar radiation rises (from 200 to 800 W) panel temperature increases from 36 °C to 92 °C, whereas variations in outside and inside air temperature have a negligible impact on the panel temperature. Thus, the use of SIRASOL is possible in locations with clear skies. Moreover, from panel temperature values we calculated mean radiant temperature and thereby the room’s operative temperature, which is proportional to the radiant panel area. When this area is 50% of the room’s floor area, operative temperature grows 3.1 °C higher than inside air temperature when solar radiation is 500 W/m². The analysis shows that a thermal asymmetry appears only when SIRASOL’s surface area to floor area ratio is higher than 32%.     

低温热水地板辐射与低温电热地膜辐射供热方式的特性分析

主要对低温热水地板辐射与低温电热地膜辐射供热方式进行分析。分析了低温热水地板辐射与低温电热地膜辐射两种供热系统的节能特性及其适应性;两种供热系统存在的问题及及其在集中供热中的应用发展前景。     

Oil shale pyrolysis kinetics and variable activation energy principle

A modified first order kinetic equation with variable activation energy is employed to model the total weight loss of Ellajjun oil shale samples. Fixed bed retort with 400 g of oil shale sample size is used in this study in 350–550 °C temperature range. Variable heating rate, h, in the range 2.6–5 °C min⁻¹ are tested.     

Performance evaluation of a radiant floor cooling system integrated with dehumidified ventilation

The radiant floor cooling system can be used as an alternative to all-air cooling systems, using the existing Ondol system (a radiant floor heating system) in Korea to save energy and maintain indoor thermal comfort. Unfortunately, a radiant floor cooling system may cause condensation on the floor surface under hot and humid conditions during the cooling season. In addition, the radiant floor system does not respond quickly to internal load changes due to the thermal storage effect of the concrete mass, which is usually present in radiant floor cooling systems.This study proposes a radiant floor cooling system integrated with dehumidified ventilation, which cools and dehumidifies the outdoor air entering through the cooling coil in the ventilator by lowering the dew-point temperature to prevent condensation on the floor surface. Furthermore, outdoor reset control was used to modulate the temperature of chilled water supplied to the radiant floor, and indoor temperature feedback control was then used to respond to the internal load changes.To evaluate the performance of the radiant floor cooling system integrated with dehumidified ventilation, both a physical experiment in a laboratory setting and TRNSYS simulation for an apartment in Korea have been conducted. As a result, it was found that the proposed system was not only able to solve the problem of condensation on a floor surface but also to control the indoor thermal environment within the acceptable range of comfort. Furthermore, the proposed system improved the responsiveness to internal load changes.     

The potential applications and advantages of powering solar air-conditioning systems using concentrator augmented solar collectors

Non-concentrated evacuated tube heat pipe solar collectors have been reported to show higher fluid temperatures with improved thermal performance in the low to medium temperature range (?60 °C) due to low heat losses but suffer higher heat losses at the medium to higher temperature range (?80 °C) which reduces their efficiency compared to concentrated evacuated tube heat pipe solar collectors. To operate as stand-alone systems capable of attaining temperatures in the range of 70-120 °C, an innovative concentrator augmented solar collector can be an attractive option. The performance of a combined low-concentrator augmented solar collector in an array of evacuated tube heat pipe solar collectors defined as concentrator augmented evacuated tube heat pipe array (CAETHPA) and an array of evacuated tube heat pipe collectors (ETHPC) were tested and compared and results presented in this paper. The analysis of the experimental data allows concluding that the use of a CAETHPA is a more efficient alternative for integrating renewable energy into buildings with higher fluid temperature response, energy collection and lower heat loss coefficient compared to the use of evacuated tube heat pipe collector array (ETHPA).     

Comparative analysis of performance and techno-economics for a H2O–NH3–H2 absorption refrigerator driven by different energy sources

The objectives of the present work are of two-folds. First, it evaluates the transient temperature performance of the H₂O–NH₃–H₂ absorption cooling machine system’s components under two types of energy sources, i.e. the conventional electric energy from grid (electric) and fuel energy from liquid petroleum gas (LPG). Results obtained have shown that performance of various components under different type of energy sources is almost coherent. For the evaporator, the system with electric supply has shorter starting time, around 6 min earlier than the system run with LPG. Meanwhile, the system powered by LPG produced a lower cooling temperature around −9 °C, compared to the system run with electric which produced temperature at around −7 °C. Economical study had been carried out subsequently, for three different energy sources, i.e. electric, LPG and solar energy (photovoltaic). From the techno-economical analyzes, it was found that the conventional electric from grid is still the best form of energy source for short-term application, as far as the present location and conditions are concerned. LPG is the next attractive energy source, especially at locations with constant LPG supply; the photovoltaic energy from solar is attractive for long term consideration since it has zero fuel cost and environmentally-friendly, but with the highest initial cost.     

A solar thermal cooling and heating system for a building: Experimental and model based performance analysis and design

A solar thermal cooling and heating system at Carnegie Mellon University was studied through its design, installation, modeling, and evaluation to deal with the question of how solar energy might most effectively be used in supplying energy for the operation of a building. This solar cooling and heating system incorporates 52 m² of linear parabolic trough solar collectors; a 16 kW double effect, water-lithium bromide (LiBr) absorption chiller, and a heat recovery heat exchanger with their circulation pumps and control valves. It generates chilled and heated water, dependent on the season, for space cooling and heating. This system is the smallest high temperature solar cooling system in the world. Till now, only this system of the kind has been successfully operated for more than one year. Performance of the system has been tested and the measured data were used to verify system performance models developed in the TRaNsient SYstem Simulation program (TRNSYS). On the basis of the installed solar system, base case performance models were programmed; and then they were modified and extended to investigate measures for improving system performance. The measures included changes in the area and orientation of the solar collectors, the inclusion of thermal storage in the system, changes in the pipe diameter and length, and various system operational control strategies. It was found that this solar thermal system could potentially supply 39% of cooling and 20% of heating energy for this building space in Pittsburgh, PA, if it included a properly sized storage tank and short, low diameter connecting pipes. Guidelines for the design and operation of an efficient and effective solar cooling and heating system for a given building space have been provided.     

Energetic performance test of an underground air tunnel system for greenhouse heating

The main objective of the present study is to investigate the performance characteristics of an underground air tunnel (UAT) for greenhouse heating with a 47 m horizontal, 56 cm nominal diameter U-bend buried galvanized ground heat exchanger. This system was installed in the Solar Energy Institute, Ege University, Izmir, Turkey. Based upon the measurements made in the heating mode, the average heat extraction rate to the soil is found to be 3.77 kW, or 80.21 W/m of tunnel length, while the required tunnel length in meters per kW of heating capacity is obtained as 12.46. The entering air temperature to the tunnel ranges from 14.3 to 21.5 °C, with an average value of 15.5 °C. When the system operates, the greenhouse air is at a minimum day temperature of 13.1 °C with a relative humidity of 32%. The maximum heating coefficient of performance of the UAT system is about 6.42, while its minimum value is about 0.98 at the end of a cloudy and cold day and fluctuates between these values at other times. The daily average maximum COP values for the system are also obtained to be 6.42. The total average COP in the heating season is found to be 5.16.     

Night ventilation control strategies in office buildings

In moderate climates night ventilation is an effective and energy-efficient approach to improve the indoor thermal environment for office buildings during the summer months, especially for heavyweight construction. However, is night ventilation a suitable strategy for office buildings with lightweight construction located in cold climates? In order to answer this question, the whole energy-consumption analysis software EnergyPlus was used to simulate the indoor thermal environment and energy consumption in typical office buildings with night mechanical ventilation in three cities in northern China. The summer outdoor climate data was analyzed, and three typical design days were chosen. The most important factors influencing night ventilation performance such as ventilation rates, ventilation duration, building mass and climatic conditions were evaluated. When night ventilation operation time is closer to active cooling time, the efficiency of night ventilation is higher. With night ventilation rate of 10 ach, the mean radiant temperature of the indoor surface decreased by up to 3.9 °C. The longer the duration of operation, the more efficient the night ventilation strategy becomes. The control strategies for three locations are given in the paper. Based on the optimized strategies, the operation consumption and fees are calculated. The results show that more energy is saved in office buildings cooled by a night ventilation system in northern China than ones that do not employ this strategy.