Experimental characterisation of a novel heat exchanger for a solar hot water application under indoor and outdoor conditions

The performance of a novel heat exchanger unit (‘Solasyphon’) developed for a solar hot water system was experimentally investigated under indoor and outdoor operating conditions. The ‘Solasyphon’ can be easily integrated to an existing single-coil hot water cylinder avoiding the need for costly twin-coil solar hot water storage. A series of tests were conducted under controlled indoor and real outdoor conditions to test and compare the performance of the ‘Solasyphon’ system with a traditional twin-coil (‘coil’) system. The analysis was based upon experimental data collected under various operating conditions including different primary supply temperatures (solar simulated); heating from ambient, heating with a partially stratified storage from ambient and finally under no draw-off and standard draw-off patterns. The outdoor testing was carried out on both systems separately over Summer/Autumn conditions in Northern Ireland. The results showed that the ‘Solasyphon’ system is more effective compared to a traditional twin-coil system for a domestic application where intermittent hot water demand is predominant and under a transient solar input particularly on intermediate or poor solar days. The ‘Solasyphon’ delivered solar heated water directly to the top of the storage producing a stratified supply at a useable temperature. The twin-coil system was found to be more efficient than the ‘Solasyphon’ system under a prolonged heating period.     

Properties and performance of advanced reflective paints to reduce the cooling loads in buildings and mitigate the heat island effect in urban areas

High reflective coatings and paints spread on the roof and walls can be very useful to reduce the cooling loads in buildings to ensure thermal comfort in the built environment. The solar reflectance of construction and cooling materials was measured with a spectrophotometer. A surface temperature monitoring campaign compared the thermal profiles of typical Italian construction materials with an innovative sustainable white paint, obtained with a special mixture of milk and vinegar of very high solar reflectance. Two building-integration cool-roof campaigns were run in the experimental building, Casa Intelligente of ENEA, in which indoor and outdoor air temperature and roof surface temperatures were monitored. This campaign, run in the summer of 2005 and 2006, allowed us to verify the influence of cool roofs to mitigate indoor air temperatures and to compare the behaviour of different cool-roof technologies.     

Passive cooling of outdoor urban spaces. The role of materials

This paper presents the results of a comparative study aiming to investigate the suitability of materials used in outdoor urban spaces in order to contribute to lower ambient temperatures and fight heat island effect. The study involved in total 93 commonly used pavement materials outdoors and was performed during the whole summer period of 2001. The thermal performance of the materials was measured in detail using mainly infrared thermography procedures.The collected data have been extensively analysed using statistical techniques. Comparative studies have been performed in order to identify the major advantages and disadvantages of the materials studied. Materials have been classified according to their thermal performance and physical properties into ‘cool' and ‘warm' materials. The impact of color, surface roughness and sizing has been analysed as well.The study can contribute to selection of more appropriate materials for outdoor urban applications, and thus assist to fight the heat island effect, decrease the electricity consumption of buildings and improve outdoor thermal comfort conditions.     

A numerical simulation tool for predicting the impact of outdoor thermal environment on building energy performance

A building affects its surrounding environment, and conversely its indoor environment is influenced by its surroundings. In order to obtain a more accurate prediction of the indoor thermal environment, it is necessary to consider the interactions between the indoor and outdoor thermal environments. However, there is still a lack of numerical simulation tools available for predicting the interactions between indoor and outdoor microclimate that take into account the influences of outdoor spatial conditions (such as building forms and tree shapes) and various urban surface materials. This present paper presents a simulation tool for predicting the effect of outdoor thermal environment on building thermal performance (heating/cooling loads, indoor temperature) in an urban block consisting of several buildings, trees, and other structures. The simulation tool is a 3D CAD-based design tool, which makes it possible to reproduce the spatial forms of buildings and constructed surface materials in detail. The outdoor thermal environment is evaluated in terms of external surface temperature and mean radiant temperature (MRT). Simulated results of these temperatures can be visualized on a color 3D display. Building heating/cooling loads and indoor air temperature (internal surface temperature) can also be simulated. In this study, a simulation methodology is described, and a sensitivity analysis is conducted for a wooden detached house under different outdoor conditions (building coverage, adjacent building height, surrounding with trees or no-trees). Simulation results show that the simulation tool developed in this study is capable of quantifying the influences of outdoor configurations and surface materials on both indoor and outdoor environments.     

The cooling performance of a radiator based roof component

Energy conservation in buildings is becoming an issue of great importance. Space cooling is getting important in most countries and different techniques have been developed one of which is radiative cooling. A prototype roof component, exploiting radiative cooling, was built and tested in the outdoor test facilities of the Centre of Renewable Energy Sources in Greece. The component comprises a radiator, which is utilizing water as the fluid medium and its cooling performance was investigated. This paper presents the construction of the component, the experimental set-up and the results taken during the monitoring procedure.     

Measured winter and spring-time indoor temperatures in UK homes over the period 1969–2010: A review and synthesis

This paper presents a review and synthesis of average winter and spring-time indoor temperatures in UK homes measured over the period 1969–2010. Analysis of measured temperatures in a sample of solid wall dwellings in the UK, conducted as part of the CALEBRE research project, is included. The review suggests that, for periods when occupation was likely, there has been little or no increase in winter and spring-time average living room temperatures over the last 40 years, with average recorded living room temperatures having been historically lower than the WHO-recommended value of 21 °C. Correspondingly, for periods of likely occupation, average bedroom temperatures appear to have increased. Compared with non-domestic buildings, there have been fewer investigations of domestic thermal comfort, either in the UK or elsewhere, and hence the paper also calls for further detailed investigations of domestic indoor temperatures during occupied hours together with thermal comfort evaluations in order to better understand domestic thermal environments. Based on suggestions from the limited range of studies available to date, living room temperatures may need to be maintained within the range 20–22 °C for thermal satisfaction, though this requires confirmation through further research. The study also emphasises that improving the energy efficiency of homes should be the primary means to effect any increases in indoor temperatures that are deemed essential. Considerations for future policy are discussed.     

Correlation of solar water heater test data

A method of correlating outdoor solar water heater test data, so that long-term average system performance can be evaluated from short-term testing is presented. The test procedure is based on monitoring the outdoor operation of a solar water heater until a range of test conditions are experienced. The procedure is shown to give reliable results for a range of cold water and thermostat set temperatures. The correlation procedure also gives consistent predictions of system performance from test data collected at test sites ranging from tropical to cold temperate climate types.     

Indoor simulation of amplitude modulated wind turbine noise

Wind energy is the world's fastest‐growing renewable energy source; as a result, the number of people exposed to wind farm noise is increasing. Because of its broadband amplitude‐modulated characteristic, wind turbine noise (WTN) is more annoying than noise produced by other common community/industrial sources. As higher frequencies are attenuated by air absorption and building transmission, the noise from modern large wind farms is mainly below 1000 and 500 Hz for outdoor and indoor conditions, respectively. Many WTN complaints relate to indoor, nighttime conditions when background noise levels are lower. As recently reported, indoor noise has the potential to cause sleeping disorders. Studies on human response to amplitude modulated WTN have been mainly focused on the outdoors, where a large amount of measured data exists. This is not the case for indoors, where it is much harder to gather data. Hence, there is a need to understand the transmission of WTN into dwellings and to develop indoor annoyance metrics. In this article, we investigate the transmission of WTN into residential‐type structures. Using an outdoor WTN recording and structures with different properties/configurations, we made a series of computer simulations for indoor noise predictions and assessed the results employing several widely used metrics for WTN, for example, spectral content, modulation depth and overall levels. In general, the indoor noise levels are higher, and the average modulation depth is similar to those of outdoor recordings. In addition, there is a significant change in the spectral shape. These results could potentially explain indoor WTN annoyance. Copyright © 2016 John Wiley & Sons, Ltd.     

SOLAR ASSISTED OPEN-CYCLE ABSORPTION COOLING: PERFORMANCE OF COLLECTOR/REGENERATORS

In this study, a side-by-side test was performed on a glazed and an unglazed collector/regenerator operating under identical environmental conditions. This test procedure differed from previous experiments in that the inlet solution state was maintained constant during the period of testing. Also, for the glazed C/R, local solution film temperatures as well as entrance and exit air dry and wet bulb temperatures were measured. With the use of experimental data, empirical correlations were developed for heat and mass transfer coefficients in terms of Nusselt and Sherwood numbers. These correlations were used in the simulation study to identify important variables affecting the performance of each collector/regenerator. The performance of the glazed collector/regenerator was considerably affected by solution flow rate, solar irradiation, ambient temperature, solution temperature and concentration at the inlet, and glazing height. The evaporation rate for the unglazed collector/regenerator was strongly dependent upon ambient temperature, humidity, wind speed, and solution concentration at the inlet to the collector/regenerator. Generally, it was found that the unglazed C/R performed better than the glazed C/R for the conditions considered in this study. Contrary to previous research, this data showed an increase in evaporation rate as the gap height was decreased from 15 to 7 cm. The glazing, also helped to maintain cleaner absorbent solution and reduced waste due to rain. © 1997 by John Wiley & Sons, Ltd.     

Survey and numerical effect analyses of the market structure and arcade form on the indoor environment of enclosed-arcade markets during summer

In South Korea, enclosed arcades have been applied to traditional markets in order to improve the physical environment of the markets. However, in some enclosed-arcade markets, occupants suffer from thermal discomfort during summer due to solar radiation overheating the indoor space. This discomfort level varies according to the market structure and arcade form.This paper presents the results of thermal surveys and temperature/humidity measurements carried out on four enclosed-arcade markets, each having a different market structure and arcade form. The paper then presents analyses of the thermal effect of the market structure and arcade form on the indoor climate. During the summers of 2003, 2004 and 2006, thermal surveys were conducted which polled responses from 156 market occupants while air temperatures and humidity levels were measured simultaneously. Numerical simulations were performed in order to evaluate eighteen different design approaches in relation to the enclosed-arcade market. The results from the temperature/humidity measurements revealed that the indoor temperature was affected by roof transmittance. In particular, in one of the four markets, where the roof transmittance was 0.7, the difference between indoor and outdoor temperatures was recorded as +4.3 °C. The occupants complained of the thermal discomfort and that much of their goods had become spoiled and discolored by solar radiation. To solve this problem, the arcade roof was eventually covered with an opaque plastic material. The results from the numerical analyses using computer simulations revealed that the transmittance of the roof material was the primary design element that thermally affected the indoor climate, followed by the ventilation opening, the roof height, and the roof type. However, the effect of the ventilation opening on the indoor climate increased as the roof transmittance increased, which created a greater temperature difference between the indoor and outdoor climates on sunny summer days.     

A novel approach to degree-hour calculation: Indoor and outdoor reference temperature based degree-hour calculation

This paper presents a novel approach to temperature probability density distribution and function. Probability density functions and frequency are successfully used in wind speed and solar energy analyses in literature. This study applies these data to temperature data analysis. The present model is developed using the indoor and outdoor temperature as a parameter. Outdoor temperature distribution is crucial for the calculation of monthly and total degree-hour. In this paper, using past weather data, the outdoor temperature probability density functions are modeled for four cities in different regions in Turkey via a new computer program. The main advantage of this approach is to allow us to determine heating and cooling loads with respect to different indoor and outdoor temperatures.     

Influence of architectural design on indoor environment in apartment buildings in Havana

The paper presents the results of research focused on evaluating the influence of the architectural design of apartment buildings located in different locations in Havana city. The object under study has been the volume of buildings in relation to their surroundings, which determines the relationship between indoor and outdoor spaces and how indoor spaces are exposed to daylight and solar radiation.Three urban areas were selected taking into account the opinion of some architectural experts. The apartment buildings were classified according to their architectural volume, considering the transitional spaces: streets and corridors, yards and indentations. Sixty six indoor spaces linked to different transitional spaces with varied dimensions, proportions and orientation were chosen to take temperature measurements and make daylight simulations.The comparative assessment of the results considered the difference between the indoor temperature and that measured in an external reference point, mainly at night, when the family is at home. The temperatures taken in the reference points confirmed the effect of the urban heat island. The best transitional space from the thermal point of view is the corridor type. On the contrary, yards offer the worse conditions, except in compact urban areas as Centro Habana.Regarding daylight, no studied space meets the minimum daylight requirement established by Cuban daylight standards, and only one achieves minimum uniformity. The best transitional space is also the corridor type, which guarantees a higher percentage of daylight with respect to an unobstructed outdoor space on a roof.Based on these results, urban form generated from detached buildings separated by corridors is more appropriate for the warm and humid climate of Havana than the compact colonial urban model, although it was considered a good option in studies carried out twenty years before. These results reinforce some conclusions reached at during the last ten years regarding the advisability of reducing land occupancy in current compact urban areas and to avoiding the use of small yards to provide daylight and natural ventilation in apartment buildings.     

Theoretical and experimental analysis of the thermal behaviour of a green roof system installed in two residential buildings in Athens,Greece

Measurements of the thermal behaviour of two residential buildings equipped with a green roof system have been performed in Athens, Greece. Experimental data have been used to calibrate detailed simulation tools and the specific energy and environmental performance of the planted roofs system has been estimated in detail. Simulations have been performed for free‐floating and thermostatically controlled conditions. The expected energy benefits as well as the possible improvements of the indoor thermal comfort have been assessed. It is found that green roofs have a limited contribution to the heating demand of insulated buildings operating under the Mediterranean climate. On the contrary, the green roof system is found to contribute highly to reduce the cooling load of thermostatically controlled buildings. For the considered residential buildings, a cooling load decrease of about 11% has been calculated. In parallel, it is found that green roofs contribute to improve thermal comfort in free‐floating buildings during the summer period. The expected maximum decrease of the indoor air and roof surface temperatures is close to 0.6°C. Such a decrease contributes to reduce by 0.1 the summer absolute Predicted Mean Vote Comfort Index levels in the building. Copyright © 2009 John Wiley & Sons, Ltd.     

Experimental study on the heat exchange effectiveness of a dry coil indirect evaporation cooler under various operating conditions

In this study, a pilot Dry Coil IEC unit, an indirect evaporation cooler established by connecting a direct evaporation cooler and a sensible heat exchanger (SHE) in series, was made, and the effectiveness data of the pilot unit were acquired under various operation conditions in an environmental chamber realizing a wide-range of indoor and outdoor air conditions. The test result shows that over 40% effectiveness can be acquired even in hot and humid climates by using the Dry Coil IEC proposed in this paper. The Dry Coil IEC reduces the cooling coil size by pre-cooling the process air during the cooling season. It can also be used as an SHE reclaiming the sensible heat from the exhaust air during winter operation. The pilot unit recovered over 60% of sensible heat in the test. In addition, a simplified model of Dry Coil IEC returning the various operation conditions was developed based on existing models of an SHE and a direct evaporative cooler. A polynomial equation returning the effectiveness of the Dry Coil IEC was derived as a function of seven independent variables highly influencing the performance of the unit. The experimental data acquired by the pilot unit operation agree well with the effectiveness values of the Dry Coil IEC predicted by the proposed model. It was also identified that the proposed equation agrees well with the existing model of the Dry Coil IEC applied to the energy simulation program.     

地板辐射与下送风复合式供冷系统运行特性实验研究

测量地板辐射与下送风复合式供冷系统运行过程中的室内空气温湿度、围护结构表面温度等室内环境参数,分析室内温湿度、热舒适性、系统换热量的变化规律,并对室内空气环境进行影响因素分析。实验结果表明:室内空气绝对湿度较室内空气温度达到稳定需要的时间更短;MRT(mean radian temperature)、OT(operation temperature)和PMV-PPD值在系统开启后第1.0 h减小速率最大,1.5 h后逐渐趋于稳定,此时,PMV约为0.49,PPD约为10%,在热舒适范围内;地板净辐射换热量、对流换热量和总换热量在系统开启后的1.5 h内递增,然后趋于稳定,此时,地板辐射换热量约为37 W/m~2,占总换热量的47%;室内空气温度和作用温度均随室外综合温度、室内发热量、供回水平均温度和送风温度的增加而增加,当室外综合温度较低或较高,或室内发热量较低,或供回水平均温度较低时,室内空气温度和作用温度变化梯度较小,室内空气温度和作用温度随送风温度增加而增加的速率近似呈线性。     

Transient model for coupled heat,air and moisture transfer through multilayered porous media

Most building materials are porous, composed of solid matrix and pores. The time varying indoor and outdoor climatic conditions result heat, air and moisture (HAM) transfer across building enclosures. In this paper, a transient model that solves the coupled heat, air and moisture transfer through multilayered porous media is developed and benchmarked using internationally published analytical, numerical and experimental test cases. The good agreements obtained with the respective test cases suggest that the model can be used to assess the hygrothermal performance of building envelope components as well as to simulate the dynamic moisture absorption and release of moisture buffering materials.     

International developments in solar thermal testing

A methodology of the design of solar energy test facilities is presented. In the design of the test facilities, careful attention has been paid to the availability of local materials and skilled labour to perform tests on solar energy equipment to international standards. Outdoor test results are presented for collector tests performed to ASHRAE standards on site in Egypt. The results are compared with indoor tests from the UK National Test Laboratory using the SERC solar simulator at University of Wales College of Cardiff, UK. Data analysis has been carried out on the outdoor and indoor results to determine the performance of these collectors. The indoor and outdoor results agreed very well. The indoor results have been corrected in accordance with International Standards to yield an ‘equivalent outdoor’ peformance characteristic. The emerging international standards for solar thermal testing are discussed, particularly in a developing country context.     

Thermal behaviour assessment of a novel vertical greenery module system: first results of a long-term monitoring campaign in an outdoor test cell

Vertical greenery modular systems (VGMSs) are an increasingly widespread building envelope solution aimed at improving the aesthetical quality of both new and existing façades, contemporarily achieving high energy efficiency performance. Within a research project, a new prototype of VGMS was developed, designed and tested. An experimental monitoring campaign was carried out on a test cell located in Turin (northern Italy), aimed at assessing both biometric parameters and energy-related issues. Two different types of growing media and two plant species, Lonicera nitida L. and Bergenia cordifolia L., have been tested on a south-facing lightweight wall. Results have been compared to the same wall without VGMS and plaster finished, in order to characterise the thermal insulation effectiveness in the winter period and the heat gain reduction in the summer period. Measured equivalent thermal transmittance values of the green modular system showed a 40 % reduction, when compared to the plastered wall, thus noticeably impacting on the energy crossing the façade during the heating season. Benefits of the VGMS are measured also during the summer season, when the presence of vegetation lowers the outdoor surface temperatures of the wall up to 23 °C compared to the plastered finishing, with a positive effect on outdoor comfort and urban heat island mitigation. Nevertheless, as far as the entering energies are concerned, not significant reduction was observed for VGMS, compared to the reference plastered wall, since the green coverage acts as a thermal buffer and solar radiation is stored and slowly released to the indoor environment.     

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.