Improve Indoor Thermal Comfort Research Articles

Experimental Study of Thermal Performance and the Contribution of Plant-Covered Walls to the Thermal Behavior of Building

This paper presented on experimental investigation of the influence of plant-covered wall on the thermal behavior of buildings in the semi-arid regions during the summer period. Thermal performance of a green walls system on facade walls has been experimentally investigated in a test room. The test cell dimensions are 1x1.2x0.8 m. In this study the thermal analysis concerns two test cells that incorporate non-covered and covered with two types of plants (Jasmine and Aristolochia). A Light source is used to simulate solar radiation. The results showed that plant cover improved indoor thermal comfort in both summer, and reduced heat gains and losses through the wall structure. It is verified that a microclimate between the wall of the test cell and the green wall is created, and it is characterized by slightly lower temperatures and higher relative humidity.

Analytical optimization of specific heat of building internal envelope

The heat storage performance of internal envelope plays an important role in improving indoor thermal comfort for a passive solar room, which is related to the thermal properties of building internal envelope. The previous researches are all case studies. The paper aims to analyze the intrinsic performance of internal envelope controlling indoor air temperature and optimize the specific heat. The results show that the optimal specific heat of internal envelope is nearly δ function which approaches to the equivalent specific heat form of phase change material. It is helpful to understand the temperature control performance of internal envelope further and guide the building material design and preparation.

Influence of Solar Radiation of External Decorative Materials on Heat Consumption of Buildings

There are many types of external decorative materials of buildings, which have different properties in absorbing, reflecting and re-radiating the solar radiation because of their different color, texture and degree of roughness. Different external decorative materials for the buildings with same direction, the amount of solar radiation will be different. The correction of heat- transferring coefficient of envelope is related not only to the direction, but also to the selected external decorative materials of buildings. In this paper, the method is to establish thermal gain or loss model of architectural envelope, to analysis the influence of solar radiation of different external decorative materials on heat consumption of buildings. Aim to provide the reference for the selection of external decorative materials in architectural design, and to improve indoor thermal comfort and reduce architectural energy consumption.

Indoor Thermal Environment Simulation of Xi'an Residential Building in Summer

Natural ventilation is an important role to improve the residential building indoor thermal environment in summer. This paper use Energy Plus to simulate indoor thermal environment and use CFD to simulate indoor air flow for Xi’an residential building, analysis the influence that different ventilation mode for indoor thermal environment factors. Then with the simulated result of PMV-PPD value to estimate indoor thermal comfort. Proved night ventilation is necessary in residential building in Xi’an and effectiveness to improve indoor thermal comfort.

To Examine the Energy Conservation Potential of Passive & Hybrid Downdraught Evaporative Cooling: A Study for Commercial Building Sector in Hot and Dry Climate of Ahmedabad

Energy consumption in the building sector is very high and it is expected to increase further due to increase in standards of living and change in typology of the building. Other major factor which has a significant effect on energy consumption is climate, especially in hot and dry climate. There is vast temperature fluctuation in such type of climate promoting greater use of air conditioning system, thus increasing energy consumption. The Study examines the energy conservation potential of the Passive Downdraft Evaporative Cooling (PDEC) technique for the commercial building sector in hot and dry region of Ahmedabad. The Study examines four different scenarios, 1) Conventional Case, 2) Envelope Design case 3) Energy Conservation Building Code (ECBC) Envelope Design case and 4) ECBC Envelope Design case with Evaporative Cooler (EC). Performance of all scenarios is measured through simulation software ‘eQuest’. Simulation results are compared with actual building observations and comparative analysis is done in terms of Cooling load, Energy consumption, CO2 emissions and other co-benefits. The Research finding proves that Passive Downdraught Evaporative cooling technique offer real opportunity for improving indoor thermal comfort conditions in a building whilst reducing cooling load of air-conditioning systems, thereby reducing energy consumption and provides better indoor environment by providing 100% fresh, cool air into a space. The analysis confirms the advantage of such passive cooling strategy in hot dry climate of Ahmedabad. Further research also identifies the significance of the integrated architectural approach.Result of the each scenario with better envelope design and efficient cooling technique has shown significant energy conservation.The findings clearly suggest that while energy efficiency can be achieved through building regulations/codes and appropriate choice of materials/construction technology, but the potential for energy efficiency is much higher when such measures are integrated into the design philosophy and approach. The results can be used to estimate the energy conservation potential of such technique for wider application and also in developing recommendations to encourage the use of such passive cooling techniques. As commercial building floor area in Ahmadabad is projected to be double by 2035[1], there is a large potential to conserve the energy. Developing guidelines and action plan to promote such techniques will certainly help to reduce energy consumption, hence reducing GHG emissions.

Performance Evaluation and Energy Saving Potential of Windcatcher Natural Ventilation Systems in China

Windcatcher as an architectural element is a passive cooling design to improve indoor thermal comfort without energy consumption. The performance and energy saving potential of using a windcatcher system in China are evaluated through EnergyPlus simulation of an oce building installed with commercial windcatchers. The simulation results for the climate condition in Beijing indicate that the peak indoor tem- perature can be reduced by more than 2 - C with the help of windcatchers, for approximately 50% of occupied hours it can meet the basic ventilation requirement and 28% of occupied hours can reach the purge demand. Moreover, 17% of cooling load can be reduced. The performance of windcatchers can be largely enhanced if they are used along with top-hung windows to create cross ventilation. Further investigations are carried out for various climate regions to evaluate the feasibility of windcatcher applications in China. It is found that according to the accumulative hours of meeting ventilation requirement, Harbin is the most suitable city for windcatcher applications and then Shanghai and Kunming. But, Kunming appears the best city in terms of percentage saving in cooling load, followed by Harbin and Urumqi. However, from the economic perspective, Beijing looks the most cost eective

Optimising Louver Location to Improve Indoor Thermal Comfort based on Natural Ventilation

Abstract Energy usage in building accounts for more than a quarter of Australia's greenhouse gas emission with space cooling alone being responsible for more than 26% of the total electrical energy usage on extreme hot days. With the goal of achieving reduction in energy usage in buildings, natural ventilation is receiving greater attention and has become an increasingly important consideration of ventilating buildings on milder days. While not being able to replace active cooling or heating systems of air conditioning altogether, a greater understanding and improvements in natural ventilation analysis techniques can widen the ambient condition at which satisfactory thermal comfort can be achieved without using active cooling and heating systems. Traditionally, natural ventilation system has been designed based on guidelines and past experiences but without any means to measure the likely outcome prior to completion of the building. In this paper, we explore a method of determining indoor flow conditions based on statistical climate data, including temperature, wind direction and wind pressure. A case study was conducted on a medium sized double storey building with an adjoining atrium. Various natural ventilation opening configurations and sizes were investigated to find the most effective and economical design. It was found that, with optimal placement of the openings, the indoor temperature can be kept to within one degree Celsius above or below of the peak ambient temperature on a critical design day. The decrease in number of hours required from traditionally heating and cooling system and implications on savings in energy bills is also discussed.

The heating effect of the additional solar house to classroom in the cold region---A case study of an elementary school

It is important to develop solar energy resource potential for improving indoor thermal comfort. In this paper, we used the statistical method to analyze observation data for temperature change in an elementary school classroom located in the clod region. The temperature data are recorded hourly in outdoor, the sunspace attached (SA), the classroom with a SA, and the reference classroom (RC) respectively. Results show that the daily mean temperature of the classroom with a sunspace attached (CAS) is higher 6.6°C than RC in the heating period. The heating effect of the sunspace is obvious during the day, while a lot of heat loses at night. To reach the indoor suitable temperature of 16°C, the fuel 315.51kgce are required, and only 61.1% of the heating requirement of the classroom are met. In order to increase the heat effect of SA, it is essential to improve the structure of the sunspace and building material properties.

Evaluation of cooling ceiling and mechanical ventilation systems on thermal comfort using CFD study in an office for subtropical region

Radiant cooling ceiling systems have already been proven to potentially provide an improved thermal comfort environment. This work conducted a full-scale experiment in an office, and a computational fluid dynamics (CFD) simulation study for a radiant cooling ceiling system integrated with air dehumidification equipment installed in this test space. The obtained results from the experiment were compared with the values from the CFD simulation to validate the accuracy of the model. Predicted mean vote (PMV) index was used to assess the original indoor thermal condition and improved conditions according to the simulation results. Experimental variables included supply air temperature from the diffuser, surface temperature, and the area of the cooling panels. In addition, diffuser position in the mechanical ventilation system was analyzed that provided suggestions on improving the design of radiant cooling ceiling panels. This study proposed solutions alongside limitations on improving indoor thermal comfort and energy efficiency using a radiant cooling ceiling system in the subtropical regions of Taiwan.

A new method to estimate optimal phase change material characteristics in a passive solar room

Due to good energy storage capacity with the large latent heat, phase change material (PCM) can be applied as interior thermal mass to improve indoor thermal comfort degree in a passive solar room. The traditional approach on the application of PCMs as interior thermal mass is case-study, by which the optimal characteristic of PCM can only be obtained based on lots of cases studied. A new and simple analytical method to get the optimal phase change temperature and latent heat of the interior PCM for a passive solar room is presented in the paper. The estimated optimization results are compared and agree well with that obtained by optimizing non-linear thermal mass in an inverse problem. It is also proved by simulation that the passive solar room with the estimated optimal PCM can reach indoor thermal comfort.

AN EXPERIMENTAL STUDY ON THE DEFROSTING PERFORMANCE OF A PCM-BASED REVERSE-CYCLE DEFROSTING METHOD FOR AIR SOURCE HEAT PUMPS

When an ASHP unit operates in heating mode, frost can be accumulated on the surface of its outdoor coil. Currently the most widely used defrosting method for ASHPs is reverse cycle defrost. However, the fundamental problem for such a method is that there is insufficient heat available for ASHPs during defrosting. This paper reports on an experimental study of developing a novel reverse-defrosting method which was thermal energy storage (TES) based on using phase change material (PCM). Comparative experiments were carried out at two operating conditions: standard defrosting condition and the PCM-based defrosting condition. Results indicated that the use of this PCM-based reverse defrosting method could help shorten defrosting time, increase defrost COP d, enhance system reliability, reduce transition duration from defrost to normal space heating operation, and improve indoor thermal comfort for occupants during defrosting and heating resumption process while without degrading the quality of space heating provided by the ASHP during heat operation.

Experimental investigation and theoretical analysis of solar heating and humidification system with desiccant rotor

In this paper, a solar heating system, which combines the technologies of evacuated tube solar air collector and rotary desiccant humidification together, has been configured, tested and modeled. The system mainly includes 15 m 2 solar air collectors and a desiccant air-conditioning unit. Two operation modes are designed, namely, direct solar heating mode and solar heating with desiccant humidification mode. Performance model of the system has been created in TRNSYS. The objective of this paper is to check the applicability of solar heating and evaluate the feasibility and potential of desiccant humidification for improving indoor thermal comfort. Experimental results show that the solar heating system can convert about 50% of the received solar radiation for space heating on a sunny day in winter and increases indoor temperature by about 10 °C. Compared with direct solar heating mode, solar heating with desiccant humidification can increase the fraction of the time within comfort region from about 10% to 20% for standalone solar heating and from about 30% to 60% for solar heating with auxiliary heater according to seasonal analysis. It is confirmed that solar heating with desiccant humidification is promising and worthwhile being applied to improving indoor thermal comfort in heating season.

Improved indoor thermal comfort during defrost with a novel reverse-cycle defrosting method for air source heat pumps

When an air-source heat pump (ASHP) unit is used for space heating at a low ambient temperature in winter, frost may be formed on its outdoor coil surface. Frosting affects its operational performance and energy efficiency, and therefore periodic defrosting is necessary. Currently, the most widely used standard defrosting method for ASHP units is reverse-cycle defrost. During a standard reverse-cycle defrosting process, the indoor coil in an ASHP unit actually acts as an evaporator, therefore, no heating is provided and hence indoor air temperature in a heated space can drop. Furthermore, a longer period of time is needed before space heating can become available immediately after the completion of defrosting. Consequently, occupants’ thermal comfort may be adversely affected. To improve the indoor thermal comfort for occupants during reverse-cycle defrosting, a novel thermal energy storage (TES) based reverse-cycle defrosting method has been developed and the improvement to occupants’ thermal comfort experimentally evaluated and is reported in this paper. Comparative experiments using both the novel TES based reverse-cycle defrosting method and the standard reverse-cycle defrosting method were carried out. Experimental results and the evaluated indoor thermal comfort indexes clearly suggested that when compared to the use of standard reverse-cycle defrost, the use of the novel reverse-cycle defrosting method can help achieve improved indoor thermal comfort, with a shorter defrosting period and a higher indoor supply air temperature during defrosting.

The impacts of ventilation strategies and facade on indoor thermal environment for naturally ventilated residential buildings in Singapore

The impacts of various ventilation strategies and facade designs on indoor thermal environment for naturally ventilated residential buildings in Singapore are investigated in this study based on thermal comfort index. Four ventilation strategies, nighttime-only ventilation, daytime-only ventilation, full-day ventilation and no ventilation were evaluated for hot-humid climate according to the number of thermal discomfort hours in the whole typical year on the basis of a series of TAS simulations. Parametric studies of facade designs on orientations, window to wall ratios and shading devices were performed for two typical weeks by coupled simulations between building simulation ESP-r and CFD (FLUENT). The results indicate that full-day ventilation for indoor thermal comfort is better than the other three ventilation strategies. With various facade design studies, it was found that north- and south-facing facades can provide much comfortable indoor environment than east- and west-facing facades in Singapore. It is recommended that optimum window to wall ratio 0.24 can improve indoor thermal comfort for full-day ventilation and 600 mm horizontal shading devices are needed for each orientation in order to improve thermal comfort in further.

Shading effects on the winter thermal performance of the Trombe wall air gap: An experimental study in Dalian

There has been little research on the application of shading devices in the air gap of the Trombe wall in China. Experiments on the thermal performance of an advanced Trombe wall with shading in the air gap was conducted in a passive solar house in Dalian. The thermal performance was investigated with regard to the simultaneous temperatures, heat gain and their acquisition of the Trombe wall. By analyzing experimental data, an investigation was carried out on the heat preservation effect by the shading device on a winter night. The theoretical optimum fixed location of the shading in the air gap for minimizing the heat loss was also discussed. Finally, the influence of shading on improving indoor thermal comfort was discussed using the concept of the building envelope response factor (BER) presented earlier by Lukic [The transient house heating condition—the building envelope response factor (BER). Renewable Energy 2003;28(4):523–32].

Methods for controlling airflow in and around a building under cross-ventilation to improve indoor thermal comfort

This paper investigates methods for controlling airflow in and around a building in order to improve indoor thermal comfort by utilizing cross-ventilation. In the first part of the study, field measurements are carried out to evaluate the effects of cross-ventilation on indoor thermal comfort. It was confirmed that a comfortable indoor thermal environment could be attained in a considerable part over summer by controlling the window opening in order to maintain the PMV value within the range −0.5<PMV<+0.5. The latter part reports on CFD predictions of flow in and around a building. The effects of planted tree arrangements around the building, openings locations and size of openings in the building are numerically investigated.

Performance evaluation of the BSRC multi-purpose bio-climatic roof

This paper reports on experimental investigation of the performance of a new multi-purpose bio-climatic roof (BCR) developed by our teamwork (The Building Scientific Research Center, BSRC). The innovative functions of this BSRC-BCR are to decrease daily heat gain through the roof fabrics, to induce significant air ventilation rate, which improves the thermal comfort of residents, to ensure appropriate daylighting without any overheating and to act as a roof radiator during nighttime. The BSRC-BCR is composed of a combination of CPAC Monier concrete and transparent acrylic tiles on the outer side, air gap and another combination of gypsum with an aluminum foil board and translucent sheets on the room side. The thermal and visual performances of BCR were investigated experimentally and compared to the conventional roof solar collector (RSC) based on the following three important parameters: the temperature difference index (TD) defined as the temperature difference between the outdoor and indoor, the air change number (ACH) induced by the BSRC-BCR and the amount of indoor illumination. To this end, two units (BCR and RSC) each of 1×1.5 m 2 surface area were integrated into the south-facing roof of the center single-room solar house of 25 m 3 volume. The experimental results show that the BSRC-BCR is extremely interesting as it can reduce roof heat gain significantly, provide sufficient natural lighting for housing and induce high air change that improve indoor thermal comfort. The TD index of BCR was always lower or close to neutral than that of RSC during the hottest period of the day. The indoor illuminance delivered by the BSRC-BCR was about 300 and 140 lx in summer and winter, respectively. The ACH was about 13–14 and 5–7 in summer and winter, respectively, two times that induced by the RSC.

PV attic ventilation: a simple tool for reducing cooling load and providing comfort

SYNOPSIS This paper investigates the performance attic ventilation, driven by photovoltaic (PV) fans, for cooling load reduction (by reducing heat gain through the ceiling) and for improving occupants thermal comfort. The ventilation fans are driven directly by a 27 Wp photovoltaic (PV) panel i.e, no battery is used. To assess the performance, two lab-scale houses each with a volume of 2.8 m3 were built using common construction materials. One of them served as a reference. Two patterns of ventilation were examined, namely external ventilation and cross ventilation. With the first, only the attic was ventilated while with the second, the ambient air was first admitted into the room and then into the attic. In addition, both non-insulated and insulated attics and those with and without a radiant barrier were considered. Tests were performed during the summer. Experimental results showed that cross ventilation could significantly reduce the heat flux transferred through the ceiling by about 3–5 W/m2. It could also ensure a high air change rate that improved indoor thermal comfort. External ventilation is mainly recommended for air-conditioned buildings.

The effect of ceiling insulation on indoor comfort

In South Africa, installing ceiling insulation in all existing houses could result in substantial benefits for the country. Simulations have shown that for high-income houses alone, almost 3000 GWh can be saved in winter heating per year. A reduction of approximately 1950 MW in the national peak demand in winter can also be achieved. These benefits are of significant economic as well as environmental importance. Unfortunately, the savings per household are too low to convince home-owners to install ceiling insulation. Other benefits, such as improving indoor thermal comfort, therefore need to be investigated. This study quantifies the summer ‘comfort’ benefits of ceiling insulation in South Africa for the first time. Results showed that three times more people would be satisfied with the indoor conditions with ceiling insulation installed than without.

Improving indoor thermal comfort by changing outdoor conditions

Recent publications in thermophysiology and biometeorology indicate that indoor climate, especially during nighttime, is quite important for well-being and avoiding physical stress by unfavourable thermal factors. In cities the indoor climate in summertime often is affected in a negative way by higher air temperatures as well as by different radiative and airflow conditions compared to non-urban areas. A multitude of investigations in urban climatology revealed that by changing some characteristics of the specific building structures (e.g., changing sealed surfaces into vegetation, especially in yards and at walls) a positive effect on the indoor climate can be achieved. By these means, the urban climate does not necessarily cause a higher thermal stress on the organism. Through interdisciplinary collaboration (meteorologists, building physicists, urban planners, architects) by relatively simple means, a significant melioration of the bioclimate for indoor conditions within cities can be achieved.