Indoor Thermal Environment Control Research Articles

Development and performance evaluation of an indoor thermal environment control algorithm incorporating MET estimation model with object detection

As people increasingly spend time indoors, the significance of the indoor environment in influencing occupant quality of life is becoming more pronounced. Traditionally, indoor environment control primarily relied on fixed temperature settings, which failed to accommodate the diverse circumstances of occupants. This approach limited the creation of a comfortable indoor environment and the enhancement of energy efficiency. Consequently, there is growing interest in occupant-centric control (OCC), which integrates metabolic rate (MET) information, which is a critical factor in determining the thermal sensation of occupants. Previously, a method was developed to estimate MET by classifying occupant poses and detecting the objects they interact with from indoor images. This study aims to develop and experimentally validate an indoor thermal environment control algorithm (ITEC-algorithm) using the MET estimation model and assess its effectiveness and applicability in real building environments.The performance evaluation revealed that the ITEC-algorithm significantly enhanced the comfort ratios, achieving improvements of up to 59% compared to the fixed temperature control and 28% compared to the control methods that only used the pose classification model for MET estimation. The energy consumption varied depending on the activity and control method, with a reduction of up to 88% compared to fixed temperature control. These results indicate that thermal comfort can be enhanced while minimizing unnecessary energy consumption by incorporating the MET of the occupants. Consequently, it has been confirmed that the ITEC-algorithm effectively improves thermal comfort by managing the MET of various occupants.

Summer Thermal Challenges in Emergency Tents: Insights into Thermal Characteristics of Tents with Air Conditioning

Emergency tents face challenges in harsh weather conditions and sometimes require the use of air conditioning for indoor thermal environment control. However, their lightweight structure makes their control methods different from conventional buildings. This study focuses on the indoor thermal environment and thermal comfort of air-conditioned tents during summer. Through experimental measurements, this study captures the distribution of air temperatures and inner surface temperatures within a tent, thus providing an understanding of the characteristics of indoor thermal environment in air-conditioned settings. Additionally, the numerical simulations conducted using the ANSYS FLUENT 2021 R1 calculate the Predicted Mean Vote (PMV) and Predicted Percentage Dissatisfied (PPD), thus contributing to a detailed analysis of the indoor thermal comfort states. The experiment revealed that the mean radiative temperature (MRT) inside the tent can exceed the air temperature by more than 10 °C. Even when the air temperature is around 26 °C, the excessively high MRT can cause occupants to feel uncomfortable, with the PMV exceeding 1.4 and the PPD surpassing 50%. Furthermore, the high MRT results in an increased demand for cooling airflow, with the cooling loss through gaps becoming a significant part in the cooling load. To ensure a comfortable thermal environment, the air-conditioning set temperature needs to be adjusted according to the weather conditions. For instance, even at the same air temperature of 35 °C, when solar radiation increases from 400 W/m2 to 1000 W/m2, the set temperature needs to be reduced from 24.7 °C to 20.7 °C. The findings of this study provide an important reference for establishing summer air-conditioning strategies for emergency tents.

The Impact of Public Green Space Views on Indoor Thermal Perception and Environment Control Behavior of Residents - A Survey Study in Shanghai

To reduce energy consumption while meeting the indoor thermal comfort requirements of residential buildings, this survey study explores the visual-thermal cross-modal effect of public green space window view on residents’ indoor thermal perception, and how this effect regulates residents’ environment control behavior. Based on an online questionnaire, 424 valid data were collected from Shanghai residents during the lockdown period during which the window view is the only accessible connection to the outside. The result shows that public green space views, while not significantly changing the physical thermal sensation of residents, made a greater proportion of participants feel thermal neutral, and significantly improved the participants' environmental evaluation, thermal comfort, and thermal acceptance, resulting in a 7% decrease in using air conditioning and 7% increase in natural ventilation. Path analysis reveals that public green space window view can improve indoor thermal comfort by enhancing subjective environmental evaluation, and thus encourage passive environmental regulation behavior, reducing energy consumption. Complementing previous studies, this research provides direct evidence for the energy-saving potential of public green space in residential areas from a different angle.
 Keywords: Visual-thermal interaction; cross-modal perception; Environment control behavior; Environmental psychology;
 Sustainable design

Experimental study on the operating characteristic of the desiccant cooling systems with the potential of condensing heat recovery

The requirement for extra regeneration heat is a significant issue limiting the energy efficiency of desiccant cooling systems. To avoid the additional energy consumption, this study analyses two systems that use condensing heat to regenerate the desiccant. The experiments for the heat pump-assisted type are executed at different indoor load profiles. A comparative experiment is carried out on a water loop-assisted type. Experimental results show that the heat pump-assisted type obtains a maximum regeneration temperature of 40.4 °C and a minimum supply air humidity ratio of 3.5 g/kg DA at the outdoor temperature below 26 °C. However, the thermal imbalance problem leads to uncontrollable indoor temperatures under 50 W/m2 load conditions. The proposed operation mode automatic switching control can improve indoor temperature by switching the system between dehumidification and cooling modes. Compared to the heat pump-assisted type, the water loop-assisted type has the same dehumidification capacity and a more stable indoor thermal environment control using high temperature chilled water above 14 °C and reduce the total primary cooling energy consumption by 58%. This study analyses the feasibility of recovering condensing heat from the perspective of thermal energy analysis, and expands the research on desiccant cooling systems without extra regeneration heat sources.

Research on a novel air conditioning system for improved indoor thermal environment control

Research on a novel air conditioning system for improved indoor thermal environment control

Development and validation of mobile app and data management system for intelligent control of indoor thermal environment

In engineering practice, air conditioning systems are not regulated according to the accurate real-time thermal sensation of occupants, which not only hinders improving the thermal comfort of the indoor environment but also wastes the energy of air conditioning systems. To introduce human thermal comfort in real-time into the intelligent control of air conditioning systems, this paper develops a mobile app and data management system for the intelligent control of the indoor thermal environment with three key components: the phone app, server and database. Function tests of the six modules are carried out to verify the stability and usability of system. A comparative experiment between wearable sensing of thermal sensation control based on this system and traditional temperature set value control under summer conditions is then conducted to verify the feasibility of the system. Under wearable sensing of thermal sensation control, the average indoor temperature setting value is 27.5 °C with an average satisfaction score of 5.50, which is higher than the average indoor temperature setting values of 26.3 °C and average satisfaction score of 4.65 under traditional temperature set point-based control. It means that the subject's thermal preference is met while achieving energy savings. The system proposed herein offers a new way to solve the problem of the disconnection between the intelligent control of air conditioning and the actual thermal sensation of occupants.

Model predictive control of indoor thermal environment conditioned by a direct expansion air conditioning system

Model predictive control of indoor thermal environment conditioned by a direct expansion air conditioning system

An optimal control method for small-scale GSHP-integrated air-conditioning system to improve indoor thermal environment control

ON/OFF controlled ground-source heat pump (GSHP) is often integrated with small-scale central air-conditioning system (ACS) for villas. Chilled-water temperature (CHWT) in this system usually oscillates in a large range due to the ON/OFF switch of the compressor. As it may be too high or too low, the cooling output of the air-handling unit (AHU) in its adjustable range may not be coincident with the indoor cooling demand, which may lead to unsatisfactory room temperature control performance. This study proposes an optimal control method for this system to improve the control robustness of the room temperature. Usually, the variation of indoor cooling-load is transferred to the chilled-water resulting in changing water temperature. In this method, the optimal chilled-water return (CHWR) temperature is calculated on the basis of the estimated sensible heat load and total cooling-load of the concerned rooms. Then, this CHWR temperature is reset following up the ON and OFF states of the compressor to regulate the variation range of the CHWT. Thus, the cooling output of the AHU in its adjustable range can always follow up the changing of indoor cooling demand. This method is tested on a simulation platform and a real ACS. The test results show good temperature control performance can be achieved. The experimental results demonstrate that the maximum deviation of room temperature is reduced by 2°C and the energy consumption of the GSHP and fan can be reduced by 30.12% at light cooling-load. The application performance shows this method can be easily realized in a common building automation system.

Application of a Novel Grey Model for Forecasting Indoor Air Temperature in Poultry Houses: Model Development

<b>Highlights</b> <list list-type=bullet><list-item> Novel grey forecasting method was proposed to predict indoor air temperatures. </list-item><list-item> Buffered rolling mechanism, period groups, and variation indices were introduced into the grey model. </list-item><list-item> Grey model could capture variation trends and air temperature fluctuation characteristics in a time series. </list-item><list-item> Proposed novel model exhibits higher prediction accuracy than traditional grey forecasting models. </list-item><list-item> Results can be adopted as a control strategy for thermal environment management for poultry production. </list-item></list> <b>Abstract.</b> The indoor climate of a poultry building is essential for the well-being and health of birds and their production performance, but achieving in-time indoor thermal environment control is difficult using the current environmental control systems that are only based on data collected by onsite sensors. Data collected by the onsite sensors can only reflect the current thermal environment conditions. Still, it cannot predict the variation trends in the environment, nor can it reflect whether cold or heat stress will occur in the livestock building. Heat and cold stress have caused significant economic losses to egg production. Predicting the indoor air temperature in poultry houses can aid in forecasting extreme air temperature, formulation of control strategies, saving energy, and reducing losses. This study proposed a novel grey model to forecast indoor air temperature, which captures the essential features of the developing trends and fluctuation characteristics. The novel model was combined with a buffered rolling mechanism, time period groups, and variation indices to enhance the accuracy; the variation indices of each time period group were inserted into each rolling process. The proposed model was employed to forecast the indoor air temperature of a poultry house; the efficacy and reliability of the proposed model were evaluated by conducting field experiments and comparing other similar forecasting models. The results demonstrated that the traditional grey model only showed a growth trend for the measured data but failed to reflect a trend with the fluctuation effect. The absolute percent errors of the conventional and novel grey forecasting models were 16.9%, 13.3%, and 6.3% in the training stage, and 26.3%, 16.4%, and 4.8% in the test stage, respectively. The buffered rolling mechanism and variation indices of each period can reflect the deviation degree in the measured data at each time point from the average trend in real-time, minimize the absolute percentage error, and improve the forecasting performance. The proposed model was superior to the traditional grey forecasting models, exhibiting a more accurate performance based on reduced error (<10%) in both the training and test stage forecasts. The proposed grey model can capture the variation trend and air temperature fluctuation characteristics in a time series. It is a helpful tool for forecasting the indoor air temperature in poultry houses.

Classification and Analysis of User Behavior based on Action Duration in Residential Split-type Air Conditioners

In residential buildings, split-type air conditioners (ACs) are important indoor thermal environment control equipment. This study focused on ACs in China’s hot summer and cold winter zone. The valid data included 196 million real-time operation log records of more than 5,000 ACs in one year. The goal of this study is to classify action duration in a quantitative and interpretable way and analysis the user behavior based on the classification of action duration. Through the human intervention by indicators and multiple-Jenks algorithm, user behaviors based on action duration were divided into 6 categories and 12 types. The comparison of these action types in mode, wind speed and setting temperature were discussed as well. It reveals that some action durations are need to be focused in different conditions.

The alternate operation control strategy between natural ventilation and air-conditioning considering delay time

Most research in the field of indoor thermal environment control has been devoted to the search for an appropriate on/off temperature of air-conditioning while relatively ignoring the energy-saving effect of the transition period length after air-conditioning turned off. We proposed a control model for the alternate operation between natural ventilation and air-conditioning to measure the delay time of natural ventilation after air-conditioning turned off. We compared the energy consumption of two cooling modes (continuous cooling and alternative operation between natural ventilation and air-conditioning) in different thermal capacity buildings in China’s hot summer and warm winter areas. Furthermore, we obtain the delay time of natural ventilation under different thermal capacity buildings. The results indicate that buildings with more thermal capacity have a greater delay time of natural ventilation. Alternative operation strategy can save at least 15% energy consumption compared with continuous air-conditioning cooling. The results are helpful to guide residents to adjust their use habits of air-conditioning according to the delay time of natural ventilation and to alleviate the pressure of air conditioning energy consumption in hot summer and warm winter areas in China.

A review of research on dynamic thermal comfort

Nowadays, people’s requirements for comfort are getting higher and higher, and traditional steady-state thermal comfort environment sometimes cannot meet people’s requirements. Dynamic thermal comfort is considered to meet people's requirements for comfort better than traditional thermal comfort, and it is also conducive to the health of occupants and building energy conservation. Therefore, this article reviews the literature on dynamic thermal comfort. First, this article briefly describes the transition from a steady-state thermal environment to a dynamic thermal environment. Next, this article reviews the research related to dynamic thermal comfort, such as the frequency of airflow fluctuations, simulation of natural wind, thermal prediction models, the use of intelligent detection equipment, and personal environmental control. This article summarizes the related research and development of dynamic thermal comfort from the aspects of dynamic airflow parameters, indoor thermal environment regulation, thermal experience, etc. This article aims to illustrate the necessity of the development of dynamic thermal comfort and its current results. The results show that under the trend of the artificial intelligence era, dynamic thermal comfort still has broad development potential. This article It can provide some research ideas for subsequent thermal comfort research. Practical application: This paper summarizes the research and development of dynamic thermal comfort from dynamic airflow, indoor thermal environment control, thermal experience, etc., and makes appropriate extensions and prospects accordingly. At the same time, the necessity of combining thermal comfort with AI trends is emphasized. This paper can provide references and ideas for thermal research on thermal comfort.

A modeling study on a direct expansion based air conditioner having a two-sectioned cooling coil

In small- to medium- scale buildings such as residences and retails located in hot and humid regions, direct expansion based air conditioning systems are widely used for the control of indoor thermal environment. However, to simultaneously control indoor air temperature and humidity using direct expansion air conditioning systems, additional and costly provisions/installation spaces are usually required. Therefore, to address the inadequacies encountered in previous related studies, based on multi-evaporator technology, a novel direct expansion based air conditioning system having a two-sectioned evaporator or cooling coil (TS-DXAC) was proposed to provide variable dehumidification capacity and improved indoor air distribution. In this paper, the development of a steady-state physics-based mathematical model for the novel TS-DXAC system is presented. The model was developed by referring to the existing sub-models for the key system components, such as a compressor, a condenser and an evaporator, which were currently available in open literature. The developed model was experimentally validated using a purposely established prototype experimental TS-DXAC system, with the differences between experimental and predicted results of less than 6%. Using the validated TS-DXAC model, a follow-up modeling study was carried out on optimizing the sizes of the two sections. The simulation results suggested that a lower surface area ratio for the two sections (Rs) can lead to a larger variation ranges of both output total cooling load (TCC) and equipment sensible heat ratio (E SHR). For example, at the inlet state of 26 °C and 50% relative humidity, when Rs was altered from 1:1 to 1:3, the variation range for TCC was increased by 33%, and that for E SHR by 51%, which was beneficial to better dehumidification.

Investigation on heat and mass transfer characteristics for a zeolite-coated heat exchanger using comparatively low-temperature energy: Heating humidification mode and cooling dehumidification mode:

Desiccant-based hybrid air-conditioning technologies are currently being developed to reduce energy consumption and enhance the effectiveness of indoor thermal environmental control in buildings. T...

Investigation on heat and mass transfer characteristics for a zeolite-coated heat exchanger using comparatively low-temperature energy: Heating humidification mode and cooling dehumidification mode

Desiccant-based hybrid air-conditioning technologies are currently being developed to reduce energy consumption and enhance the effectiveness of indoor thermal environmental control in buildings. The purpose of this study is to propose a compact desiccant-based outdoor air-conditioning system that directly uses heated desorption and cooled adsorption with comparatively low-temperature energy, and to propose a mathematical model for the system by investigating the heat and mass transfer characteristics of a zeolite-coated heat exchanger (ZCHE). To study the heat and mass transfer characteristics of the ZCHE, the moisture removal capacity and the moisture removal regeneration were measured at various heat source temperatures and water flow rates using an experimental model. The measured values were adopted as boundary condition for mathematical model. The results show that the air-conditioning performance of the ZCHE is strongly dependent on the water temperature under constant air conditions. The humidification capacity of the ZCHE was measured 25.0 g at 5 kW heat capacity and the humidification capacity was measured 10.2 g at 0.6 kW cooling capacity. The relative errors of mass transfer coefficient and heat transfer coefficient are ±3.6% and ±3.8%, respectively. Moreover, the proposed mathematical model fitted well with measured values.

Experimental Research on Indoor Thermal Environment Control and Work Efficiency

In order to explore the relationship between work efficiency of office staff and human thermal sensation index PMV, in this paper, the method of combining experimental test and subjective evaluation is adopted to bring seasonal preference into the research scope of work efficiency, and the experimental data are analyzed by quadratic regression. It was found that the highest working efficiency of indoor staff did not appear in the thermal neutral state, but in the preferred environment. Subjects preferred slightly warm indoor environment in heating season and slightly cool indoor environment in transition season. This paper can provide some reference value for the study of the factors affecting the work efficiency of indoor staff.

Indoor Thermal Environment Control System Based on Maximum Work Efficiency

Based on the indoor thermal environment on the influence of the office personnel work efficiency on the basis of experimental research. In this paper, a control method based on maximizing work efficiency is proposed, which aims at maximizing indoor staff’s work efficiency and rest efficiency, and takes Predicted Mean Vote (PMV) as control parameter to control indoor environment, taking into account the requirements of comfort. The operation effect of the control method based on maximum work efficiency is estimated. It is found that compared with the traditional control system based on PMV index, the system not only improves the work efficiency and rest efficiency of indoor personnel, but also is more comfortable. The indoor environment control system based on maximizing work efficiency is still in the theoretical stage. The construction and actual operation effect of the system need to be further studied.

A thermal environmental model for indoor air temperature prediction and energy consumption in pig building

Indoor thermal environment is a critical factor for animal health and production in confined livestock facilities. In order to improve indoor thermal environment control and save energy, a novel dynamic thermal exchange model was developed using the energy balance equation (EBE) and 87 days of data collected in three different seasons in a pig building to simulate the heat transfer and energy consumption in the building. To evaluate the performances of the EBE model, a comparison was made using adaptive neuro fuzzy inferring system (ANFIS) for indoor air temperature prediction. Also, the EBE model was evaluated comparing its outputs of indoor temperature with the dataset of six days, under three different ventilation modes (Min-vent, Low-vent, and High-vent) that represent for the cold, warm and hot weather, obtained through a monitoring period in pig buildings during the production. The results showed that, under three different ventilations modes, the maximum errors between the EBE model simulated and measured data were 1.5 °C compared with 2.6 °C of the ANFIS model; and the averaged coefficients of determination R2 were 0.945 and 0.743, respectively, for the EBE and ANFIS models. Compared with the present ventilation operation, there was 358.301 kW h power saved with the EBE model in a pig room during the whole research period of 87 days. Therefore, this research has several practical applications: the model can be used in developing strategies of indoor thermal environmental control, it can also increase the knowledge about energy consumption in the livestock house.

Research on Indoor Thermal Environment Control and Thermal Sensation Prediction

Most of indoor thermal environment are controlled based on given values. Researchers have proposed a new indoor thermal environment control method based on thermal sensation. Thermal sensation means human body thermal sensation to indoor thermal environment such as cold and hot. This method can not only avoids the unreasonable setting points, but also satisfies the demand of dynamic thermal comfort. At the same time, it benefits to thermal comfort and energy saving of building. Since there are many factors influencing human body thermal comfort, this method needs to be supported by more experiments. This article discusses on the thermal sensation influence factor of this new method, which will make more energy saving.

Research on Energy Saving Potential of Indoor Thermal Environment Control based on Thermal Sensation

Most of indoor thermal environment are controlled based on given values. Researchers have proposed a new indoor thermal environment control method based on thermal sensation, thermal sensation means human body thermal sensation to indoor thermal environment such as cold and hot. This method can not only avoids the unreasonable setting points, but also satisfies the demand of dynamic thermal comfort. At the same time, it benefits to thermal comfort and energy saving of building. This article makes a deep research on energy saving potential of this new method, which will make more energy saving.