Provide Indoor Thermal Comfort Research Articles

Indoor thermal comfort assessment using different constructive solutions incorporating PCM

Sustainable energy and thermal retrofit design of buildings or districts has a strong global impact in the viewpoint of economies and energy-efficiency perspectives. Several aspects such as architectonic design, building materials, construction technology, mechanical systems and outdoor climate determines the thermal behaviour of buildings and their ability to provide indoor thermal comfort to occupants. The use of geothermal energy and phase change materials (PCMs) in the construction systems are an opportunity that may attenuate indoor air temperature fluctuation as well as overheating risk. This paper presents the results of a study on indoor thermal comfort and energy efficiency regarding the PCM’s positive role when applied to new constructive solutions, inside a building with a geothermal system linked to the air conditioning system. The PCM study was based on real and simulated investigations in two rooms of a new university department at the Aveiro campus. Higrothermal monitoring (indoor air temperature) of two rooms in which one of them has PCM panels incorporated into gypsum board partition wall and into a suspended ceiling. The scope was driven to investigate the potential of these solutions for overheating mitigation. The numerical study was conducted by using an evolutionary algorithm coupled with the software EnergyPlus® used in simulations. In the scope of this optimization process, constructive solutions with the incorporation of different types of PCM with different melting temperatures and enthalpy, and different flow rates of natural ventilation were combined to investigate the potential and the payback time of these novel solutions.The results for the room measurements show that the indoor thermal comfort of the rooms, present long periods of discomfort namely in overheating. However, it was proved that the PCM application in one of the rooms lead to an overheating reduction of 7.23% representing a PCM efficiency of 35.49%. After the optimization process an overheating reduction of about 34% was attained by the use of PCM in one of the rooms. Regarding the economic analysis of the use of the PCM for cooling demand reduction, a payback time of 18years was attained.

Vernacular architecture as an idiom for promoting cultural continuity in South Asia with a special reference to Buddhist monasteries

Architectural style is a medium for the promotion of cultural identities and cohesion. South Asian Association for Regional Cooperation (SAARC) nations provide a prism through which all forms of vernacular architecture can be viewed. This study is presented through the lens of the soul of the eye coupled with the power of technological probing. This synthesis affords a most appealing and lyrical exploration of the course of the development of cities within the SAARC nations. It showcases research results combining the above stated synergy—starting from some of SAARC’s sophisticated historic cultures, cultures that ebbed and flowed along its shores and valleys. This paper shall touch upon unique cultural roots stretching back to the Dravidian civilization that flourished over 3500 years ago and also look at the grouping of houses within the Indus Valley Civilization in Lothal and the Sarasvati Valley Civilization in Kalibangan. The sensitivity underlying SAARC architecture and its traditions are seen in many communal settlements, profoundly so in the Indian subcontinent and in Sri Lanka. The paper shall showcase two specific, but nevertheless, distinct styles of communal functioning within unique architectural strongholds in the ancient Ratnagiri University in Odisha, India, and also touch upon a unique blend of styles of landscape architecture in Sri Lanka. The overarching emphasis of this study is that throughout SAARC’s history, architecture has been creatively adopted to the need of its users and the characteristics of its climate and location. It has always fulfilled the needs and nourished the spirit of its people, promoting cultural cohesion even today. In this context, it is interesting to explore traditional techniques of vernacular architecture in houses in Andhra, Tamil Nadu and Kerala. The common thread linking mass housing in Lothal, Kalibangan, Anuradhapura and Ratnagiri about 2 millennia ago, with present day housing patterns, is in the application of sustainable building practices using intelligent building forms, fabric and orientation. This paper explores this commonality from a modern perspective using CFD. As the SAARC countries still struggle to get a fuller understanding of their unique ecology and the complexity of their diverse cultures, revisiting the architectural legacy of their indigenous societies might prove insightful. The need for this revisit becomes even more relevant in the wake of the Paris Agreement and more recently the Kigali Agreement. The discourse on providing indoor thermal comfort to the SAARC people cannot be decoupled from the climate change story—heating, ventilation and cooling consume a large amount of energy and have a deep underlying link with the targets set at Paris and Kigali. The onus will be on a large number of stakeholders to meet these targets—engineers, architects, manufacturers, policy-makers, researchers and consumers. This paper aims at reminding the stakeholders of the richness and the usefulness of their vernacular architecture in upholding the ideal of sustainability.

Low cost humidity controlled air-conditioning system for building energy savings in tropical climate

The viable solution to the high latent load that naturally occurs in tropical regions requires an alternative system that runs at relatively low energy consumption yet be able to provide indoor thermal comfort by effective handling of the excessive humidity. Although the existing outdoor air treatment system is a proven approach, it is unpopular in developing countries due to its high initial cost. In this paper, a new system termed Dual Air Handling Unit system is proposed to be the answer. The function of Humidity-control Air Handling Unit is to remove the moisture from the conditioned room up to the desired humidity level and in the process the room temperature is also fractionally reduced. The Temperature-control Air Handling Unit completes the task by removing the remaining sensible heat so that the room temperature is maintained at the required set-point. By reducing the relative humidity to 50%, a much lower value than that of the normal air-conditioning could offer, room temperature of the new system is shifted higher to 26°C in order to reduce the energy consumption. The simulation result shows that the proposed system offers energy savings up to 13.2% compared to the conventional air-conditioning system, without compromising the thermal comfort of the occupants.

Ventilation in Termite Mound: New Solution for Follow in Architecture

The airflow in building environment is a strategy that could provide indoor thermal comfort conditions in warm and dry environment. Therefore, formation of ventilation inside buildings is essential. In the meantime, the nature has some structures, which have created much potential in the natural ventilation. Thus, this research aims to provide a mechanism for improving natural ventilation in the building to recognize the effective features in the termite mound, as a successful natural structure in hot and dry climate. In order to conduct this research, extensive examples of termite mounds were studied, which were located in the hot and dry climate. The research tool was the library studies carried out so far in the field of biology, which provide strategies to promote natural ventilation system in the building after recognizing the process of termite mound ventilation and its effective factors. The results indicate that wind, water, temperature differences, and the form of inner channels of the mound have an important role in natural ventilation. These factors require vertical ducts inside the building in order to streamline the air. However, other features such as the materials applied in the termite mound and placing in the ground reduce the heat dissipation inside mound building, but these features have no effect on the process of natural ventilation inside the mound.

Effects of Heat Loss/Gain on the Transient Testing of Heat Wheels

Heat wheels are used in ventilation systems to provide indoor thermal comfort by recovering considerable amount of sensible energy from exhaust airstream. The transient single step test is a new testing method developed to determine the sensible effectiveness of heat wheels. In practice, heat loss/gain may create large uncertainty in the sensible effectiveness obtained through the transient testing. In this study, the transient analytical model in the literature is extended to account for heat loss/gain effects in the transient testing. The results state that in particular operating conditions, the sensible effectiveness can be affected by more than 10% due to heat loss/gain. A new testing facility is developed to investigate the effects of heat loss/gain on the sensible effectiveness through transient testing of a small-scale heat exchanger. After decoupling heat loss/gain effects from transient test data, less than 2% difference was observed in the sensible effectiveness while supply and exhaust flow rate was small (Re < 209) and the temperature difference between them was ΔTst < 7.0 °C. However, the sensible effectiveness decreased more than 9% while ΔTst > 37.5 °C or Re > 600. An empirical correlation was proposed based on the transient test data that correlates the sensible effectiveness with the heat capacity rate ratio. Comparing the results of proposed correlation with literature, less than 2% difference was observed at the heat capacity rate ratio of greater than 0.5 after the heat loss/gain effects were decoupled from transient test data.

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

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

Investigation of Iranian traditional courtyard as passive cooling strategy (a field study on BS climate)

Abstract The use of passive systems for climate control in providing indoor thermal comfort minimizes global trends in increasing the energy demand for active systems of climate control which has unacceptable negative impacts on the natural environment. This concept is ignored for designing of contemporary buildings which care less about the environmental impacts. The main objective of this study is to investigate the concept of the traditional central courtyard as a passive cooling strategy for improving indoor thermal comfort in the BS climate of Iran. An empirical field study was conducted to analyze three important courtyard design variants including orientation, dimensions and proportions, as well as opaque (walls) and transparent surfaces (windows), in fourteen valuable traditional houses in five ancient cities located in the BS climate of Iran. Results of this quantitative study, show that Iranian traditional central courtyards were designed based on a careful attention to orientation and geometrical properties regarding the physical and natural parameters to act as an effective passive cooling system. In conclusion, all data sets were integrated to propose a physical–environmental design model for central courtyards as a useful passive strategy which can be generalized for the wider use of environmentally sustainable design principles in future practice concerning courtyards for buildings in BS climate.

HVAC system design under peak load prediction uncertainty using multiple-criterion decision making technique

Heating, ventilation and air-conditioning (HVAC) systems are widely equipped in modern buildings to provide indoor thermal comfort and guarantee indoor air quality. In a conventional design, the components of an HVAC system are sized according to a deterministic peak load, predicted according to typical weather condition, building physics and internal load. It has been shown by many studies that this prediction is associated with uncertainties since building physical parameters cannot be accurately set and the weather and the internal load used in the design may be different from the real situation after use. Therefore, uncertainty cannot be neglected in order to properly size a HVAC system. In this paper, a prototype of HVAC system design under uncertainty is proposed, which is able to take uncertainty directly in the design, and most importantly it can assess the performance of a design at the design stage in term of multiple performance indices and the customers’ requirements and preferences, i.e. the new design method falls in the framework of multiple criteria decision making. Case studies are used to illustrate the design procedure, and the result is compared with that of a conventional design method.

Bioclimatic chart analysis in three climate zones in Cyprus

The concept of bioclimatic design is based on the development of an architectural design adapted to environmental conditions. The utilization of the favourable climatic elements can offer to the users, indoor thermal comfort conditions and at the same time it minimizes the energy consumption which is needed for heating and cooling. This paper provides the bioclimatic analysis for three different climatic zones in Cyprus, coastal, inland and mountainous. The building bioclimatic charts of V. & A. Olgyay are used to examine whether passive strategies can provide indoor thermal comfort in the buildings in these zones. The results of bioclimatic charts are studied in conjunction with the climatic data for the three climatic areas. These are compared and investigated in order to find whether there is sufficient amount of solar radiation for passive heating needed to achieve thermal comfort during winter. The study concludes to a preliminary guide of passive design strategies for buildings, as an outcome of the bioclimatic charts analysis for coastal, inland and mountainous zones in Cyprus. The results can be used for locations with similar climatic conditions.

Recent Developments of Advanced Fuzzy Logic Controllers Used in Smart Buildings in Subtropical Climate

Building management system (BMS) has the ability to monitor and control buildings’ mechanical and electrical equipment including namely heating, ventilating and air conditioning (HVAC), lighting, power, fire and security systems. BMS can also provide indoor thermal comfort within commercial buildings including industrial and institutional buildings and able to reduce energy consumption. However most of HVAC systems are controlled by using conventional controller whose functions are based on ON/OFF controller and Proportional-Integral-Derivative (PID) controllers. These controllers are not the ultimate solution to save energy because the operations of HVAC systems are nonlinear. Thus, the implementation of fuzzy logic controllers within smart buildings will be more efficient which consequently will save more energy and money. This paper reviews, investigates and evaluates the use of fuzzy logic controller in HVAC systems and light controllers for smart buildings in subtropical Australia. Additionally, it highlights the recent developments in BMS controllers including its conceptual basis, capabilities and limitations.

Distributed MPC for Green Thermally Comfortable Buildings Based on an Electro-thermal Modular Approach

Abstract The aim of the paper is to present a demand-side management approach that uses a distributed model-based predictive controller to provide indoor thermal comfort in buildings with a limited green energy resource. The overall system predicts the indoor environmental conditions for buildings with different plans that are modeled using an electro-thermal modular scheme. For control purposes, this modular scheme allows an easy modeling of buildings with different plans where adjacent areas can thermally interact. The control system selects the most appropriate actions to satisfy the comfort and power constraints. In a distributed coordinated environment, the control uses multiple dynamically coupled agents (one for each subsystem/zone/house) aiming to achieve satisfaction of available energy coupling constraints. The distributed environment is simulated with two houses with different plans, one house with two divisions and the other with one. The results validate the proposed methodology in terms of both thermal comfort and energy savings.

Neural computing thermal comfort index PMV for the indoor environment intelligent control system

Providing indoor thermal comfort and saving energy are two main goals of indoor environmental control system. An intelligent comfort control system by combining the intelligent control and minimum power control strategies for the indoor environment is presented in this paper. In the system, for realizing the comfort control, the predicted mean vote (PMV) is designed as the control goal, and with chastening formulas of PMV, it is controlled to optimize for improving indoor comfort lever by considering six comfort related variables. On the other hand, a RBF neural network based on genetic algorithm is designed to calculate PMV for better performance and overcoming the nonlinear feature of the PMV calculation better. The formulas given in the paper are presented for calculating the expected output values basing on the input samples, and the RBF network model is trained depending on input samples and the expected output values. The simulation result is proved that the design of the intelligent calculation method is valid. Moreover, this method has a lot of advancements such as high precision, fast dynamic response and good system performance are reached, it can be used in practice with requested calculating error.