Air Temperature Control System Research Articles

Experimental and numerical investigation of the effects of passive radiative cooling-based cool roof on building energy consumption

Passive radiative cooling is an energy-efficient method that reduces indoor temperature and cooling load in buildings, thus contributing to significant energy savings. This study investigates the thermal performance of the passive radiative cooling-based cool roof (PRC-CR) based on experimental and numerical analysis in terms of indoor air temperature and space cooling load indicators. Two experiment rooms constructed from concrete are developed with an indoor air temperature control system. One is the PRC-CR room with the roof covered by a passive radiative cooling metamaterial and the other is the reference room with a concrete roof. Long-term testing results in Hefei show that the indoor air temperature of the PRC-CR room is 5.5 °C lower in maximal and 1.8 °C lower on average than that of the reference room in summer when the indoor air temperature control system is off. Besides, when the indoor air temperature control system is switched on, the PRC-CR room achieves a 29.1% reduction in daily cooling load in summer and a 4.1% increase in daily heating load in winter, which suggests that passive radiative cooling can indeed save energy in cooling season (i.e., hot season) but cause overcooling in heating season (i.e., cold season). In addition, a simulation building model is developed to further investigate the effect of the PRC-CR on the energy consumption of buildings in different locations. The predicted results show that PRC-CR reduces the total load of buildings in cooling load prevailing regions (e.g., tropical zones, subtropical zones, and the vast majority of warm temperate zones), while increasing the total load of buildings in heating load dominant regions (e.g., most middle temperate zones, cold temperate zones, and plateau climate zones). In summary, this work demonstrates both the positive and negative effects of PRC-CR, providing valuable insights into PRC-CR applications.

A two-degree-of-freedom controller for a high-precision air temperature control system with multiple disturbances

The key equipment to prevent precision machinery such as lithography from being influenced by air temperature fluctuation is a high-precision air temperature control (ATC) system. The ATC system developed for a lithography immersion testing platform suffers from the difficulties of multiple disturbances, large inertia and time delay. However, seldom have control methods can solve these problems systematically. A two-degree-of-freedom (2DOF) controller is proposed in this paper for this system, where model predictive control (MPC) is developed to overcome large inertia and time delay in the main control loop, and the measurable disturbance from the inlet air is compensated; based on the loop shaping approach, the controller in the disturbance rejection control loop is designed to attenuate the load disturbance; a Kalman filter is designed to reduce the influence of noise having no stable frequency characteristic. The experimental results show that the MPC controller and Kalman filter can effectively avoid the system oscillation, and the disturbance rejection control loop can significantly attenuate the load disturbance in the frequency range from 0.01 to 0.02 rad/s. Therefore, the 1σ precision is increased by 3.3 mK to 8.7 mK by the 2DOF controller when the system is influenced by the load disturbance with different fluctuation amplitudes.

TFNet: Few-shot identification of LTI systems based on convolutional neural networks

Recent research in system identification aims to reduce the amount of data required for identification and the persistence of excitation while maintaining the identified model’s generalization and goodness of fit. This paper introduces TFNet11TF stands for Transfer Function. as a few-shot transfer function identification method for industrial systems. TFNet enables both structural and parametric identification of industrial linear time-invariant systems from their pulse response. Furthermore, TFNet identifies properties such as the existence of integrator and non-minimum-phase zeros in systems, as long as the order of the system is two or smaller. We compare the performance of TFNet with that of classical and state-of-the-art rival methods on syntactic data, where TFNet outperforms other methods by a wide margin. Furthermore, experiments on two laboratory setups: an air temperature control system and a two-tank control system demonstrate that TFNet estimates a close model to the ground truth despite colored measurement noise in the first experiment, and without driving the system out of its operating point in the latter case.22The python implementation of TFNet is in https://github.com/abbasnosrat/TFNet.git.

Cloud-based Design of the Intake Air Temperature Control System

Cloud-based Design of the Intake Air Temperature Control System

НЕЧІТКА ЕКСПЕРТНА СИСТЕМА ДЛЯ КЕРУВАННЯ ТЕМПЕРАТУРОЮ ПОВІТРЯ У ПРИМІЩЕННЯХ ТОРГОВЕЛЬНО-РОЗВАЖАЛЬНОГО ЦЕНТРУ

Abstract The article presents the stages of developing a fuzzy expert system for the operator of a heating point of a shopping and entertainment center. The principle of operation of the air heating system of the mall is shown, implemented using computer-integrated control with a SCADA system. For the effective operation of the air temperature control system in different areas of the mall, functions for belonging to comfort zones have been developed in terms of visitors and the requirements of sanitary standards. It is indicated that typical air temperature stabilization controllers cannot always provide the desired mode due to the influence of a large number of uncontrolled disturbances on the control system. In this case, in the absence of additional blocks for adapting control algorithms, it becomes expedient to remotely control the operator using a mnemonic diagram of the ventilation process. And to improve the efficiency of the process of remote control of thermal equipment, an expert system was proposed that implements the algorithm of I. Mamdani, to control the coolant flow valves. The controller receives information from the outdoor air and air temperature sensors in the control area of the mall. After processing the signals from the sensors, the controller transmits information to a computer with an expert system. Depending on the temperature and season of the year, the program calculates the optimal position of the valve (in percentage of stroke) for the flow rate of the coolant and recommends installing it to the operator. Also, it is shown that in the process of developing a fuzzy expert system, it is recommended to choose the Gaussian type of membership functions; minimal number of terms - sets - three functions of dependency; weight coefficient of each rule in the knowledge base is the same and equal to 100; the method of defasification is the method of the center of gravity. It is indicated that the introduction of expert advice to operators can also lead to a reduction in the response time to emergency situations up to 90% increase in the reliability of the equipment as a whole.

Cloud-based Design of the Intake Air Temperature Control System

Cloud-based Design of the Intake Air Temperature Control System

High-precision air temperature control considering both hardware elements and controller design

The environment with high-stability temperature is crucial for precision machinery such as lithography and laser interferometer. Some studies have investigated temperature control algorithms and temperature fluctuation attenuators to provide precision temperature control systems for them. In this paper, considering the characteristics of hardware elements and the closed control loop overall, a general control loop connected by multiple cascade loops is proposed for high-precision air temperature control to reject the disturbance from the inlet air. It is found that this disturbance and the noise generated by the non-uniform air temperature of the chamber are the two main sources affecting the control precision. Based on loop shaping, a controller with compensators is designed for the cascade control loop to make a tradeoff between the disturbance rejection and noise attenuation. The lumped parameter theoretical models of three kinds of attenuators for air temperature fluctuation are analysed for the design of precision air temperature control. An air temperature control system is used to verify the performance of the proposed controller. The results demonstrate that the controller can improve the disturbance rejection performance while reducing the sensitivity to the noise. The 1 σ derivation of the chamber air temperature is decreased from 15.6 mK to 10.5 mK.

Automation of temperature control of a heat generator with a fuzzy logic controller

Purpose. Improving the quality of temperature control of a heat generating installation for air heating. Methods. The specificity of the issue under consideration determines the analytical method of research by formulating a mathematical model of the non-stationary thermal regime of the heat generator and calculating the parameters of the temperature controller based on fuzzy logic. Results. Analysis of the thermal effects of a heat generator with a heat exchanger, a physical model is determined and, on its basis, a mathematical model of non-stationary heat transfer in the elements of the heat generator design is formulated. The model is presented in the form of three partial differential equations. An approximate solution of the system of equations and generalized simplifications made it possible to determine the dynamic model by means of first-order aperiodic transfer functions with delay. Based on the identified model coefficients, a fuzzy controller rule base and an automatic temperature control system were created in two versions: with a typical PID controller and a fuzzy temperature controller. The analysis of transient processes of regulation of the automatic temperature control system was carried out. Conclusions. An analysis of the characteristics of the transient process of the automatic temperature control system revealed that the control time of a system with a fuzzy controller is less than in a system with a typical PID controller. Therefore, a fuzzy air temperature control system in a heat generator can be used to automate a significant class of heat generating devices. Keywords: heat generator, fuzzy controller, dynamic mode, mathematical model, production room.

CFD model for tubular SOFC stack fed directly by biomass

The energy transition can also be promoted by the sustainable use of biomass. Residual biomass in the Mediterranean areas can be exploited to a greater extent through highly efficient fuel cell systems. The Direct Biomass-SOFC project is based on a direct coupling between biomass power supply and SOFC tubular cells. This research project stems from the need to cover the electricity demand, avoiding the use of non-renewable sources. It will be investigated the unused or little-used biomass sources that can be exploited from the Mediterranean area.To this purpose, analyses were conducted to model a SOFC tubular cell stack by investigating the optimal configuration. The basic objective is to design a SOFC tubular cell stack, fed by syngas to produce at least 200 W. Two configurations were chosen: a square and a circular arrangement. Another objective of the study is to choose the best temperature control system. It have been selected a pressurised water system and an air system. The results show that the best performance is guaranteed by a square arrangement with an air temperature control system. The circular configuration provides less power than the square configuration, being limited by the multiple series connection to the lowest current value. The maximum electrical power produced with the square configuration is 225 W.

APPLICATION OF AUTOMATION PLANTING SYSTEM AT GREEN HOUSE IN IMPROVING PLANT QUALITY

Research has been done to application of automation planting system at green house in improving plant quality which aims to help facilitate the work of farmers and get maximum crop yields. In this case Green House is simulated using acrylic boards with an area of 80 cm × 50 cm × 50 cm. The component used to detect temperature and humidity is the DHT 11 sensor. The air temperature and humidity control system is carried out by fans and incandescent lamps. Then for watering plants based on the time read in real time used Real Time Clock DS1307, and for soil moisture sensor used sensor YL-69 where soil moisture on the sensor is 0-100%. All data will be displayed on the LCD display 2 × 16. System testing is conducted by observing the system function in some time conducted from 05.00 am to end at 17.30 pm. At 07.05 and at 17.02, the watering of plants will be done in all directions. If the DHT 11 sensor detect a temperature above 32°C, the microcontroller activates the ventilation and peltier fans to neutralize the temperature inside the green house. Whereas if the temperature is detected below 27°C and above 26°C then lamp 1 will turn on and if the temperature is below or equal to 26°C then lights 1 and 2 will be activated until the temperature returns to normal which is between 27°C - 32°C. Last testing, if the sensor reads soil moisture below 60% then watering of plants will be done to the detected dry soil.

Development of Solar Assisted Multi-Crop Dryer

Appropriate technology for the conversion of solar radiation to thermal energy is vital for food dehydration. Solar drying considered an advancement of sun-drying is an efficient solar energy system. A reliable and low-cost multi-crop solar drying technique is required for small scale farmers in Sri Lanka. Therefore, the objective of this study was to develop a solar heater assisted multi-crop dryer for small scale farmers. The main components of solar dryer are flat plate solar collector, drying chamber, solar panel with air DC heater, turbo ventilator, exhaust fans, and temperature control system. The performance of the fabricated solar assisted multi-crop dryer with DC air heater was evaluated for drying rate and drying efficiency of three agro-products; bitter gourd (Momordica charantia), jackfruit (Artocarpus heterophyllus) and mushroom (Pleurotus ostreatus). The drying rates were 0.151 kgh-1 for bitter gourd, 0.145 kgh-1 for jackfruit, and 0.154 kgh-1 for mushroom. The efficiency of solar collector was 25.84%. The drying efficiencies for bitter gourd, jackfruit, and mushroom were 12.85%, 12.35%, and 13.15%, respectively. Further, favorable colour could be achieved by the modified solar assisted multi crop dryer. Therefore, the solar assisted multi-crop dryer designed in the present experiment is an effective method of converting solar radiation to thermal energy and could be recommended for small scale farmers in Sri Lanka for drying agro products. Further improvements are required to increase solar thermal efficiency.

Особливості розробки інтелектуальних систем керування виробництвом ентомофагів

The article reveals the features of the development of intelligent control systems for the production of entomophages, the relevance of the selected research area is determined. The aim of the study was to substantiate the feasibility of using intelligent control systems in the production of entomophages. Object of research – management process the cultivation of caterpillars Ephestia kuehniella in a specialized box in the production of entomophage Habrobracon hebetor. Research methods – systems approach, data mining, semantic modeling, situational management. A structural diagram of a hybrid intelligent system for controlling the air temperature of a box for growing entomocultures has been developed; knowledge representation model in relation to the construction of a hybrid intelligent control system in the form of a predicate semantic network. The production rules of the knowledge base of the intelligent control system have been developed, which allow to clarify the process of its creation. At the same time, attention is focused on: the sequence of formation of the training sample, which affects the accuracy of control of the air temperature of the box and, accordingly, the costs of electricity; use of ANFIS-editor MATLAB, which developed a self-learning neural network that automatically created a knowledge base regarding dependency the temperature setting of the meter-controller from the error of air temperature regulation. The expediency of using intelligent control systems in the production of entomophages has been scientifically substantiated. Formalized process of creating a hybrid intelligent box air temperature control system for growing entomocultures in the form of a predicate semantic network using production rules. The abovementioned makes it possible to systematize knowledge in relation to the processes of managing the production of entomophages, improve energy efficiency and the level of automation of the production process, which has a positive effect on both the state of the biological component of the object and the economy of the enterprise. The research results were introduced in the laboratory production of the entomophage Habrobrakon hebetor.

Alleviation of Field Low-Temperature Stress in Winter Wheat by Exogenous Application of Salicylic Acid

Low temperature in later spring severely limits plant growth and causes considerable yield loss in wheat. In this study, the impacts of exogenous salicylic acid (SA) on plant growth, grain yield and key physiological parameters of wheat plants were investigated under field low-temperature conditions using a field air temperature control system (FATC). The results showed that low-temperature stress significantly decreased leaf net photosynthetic rate, plant height and biomass production of wheat plants at the jointing stage, resulting in a reduction in grain yield. Moreover, the growth period of wheat plants was prolonged by low-temperature stress. However, SA-treated plants significantly improved the photochemical efficiency of photosystem II, accumulation of osmo-protectants, activities of enzymatic antioxidants, and pool of non-enzymatic low molecular substances compared with non-SA-treated plants under low-temperature stress. Pretreatment with SA effectively alleviated low-temperature-induced reduction in leaf net photosynthetic rate, plant height, biomass production and grain yield as well as prolonging of growth period of wheat plants. However, SA-treated plants had no significant effects on the expression levels of cold-responsive genes compared with non-SA-treated plants under low-temperature stress. Our results demonstrated that exogenous application of SA is an appropriate strategy for wheat to resist late spring low-temperature stress under field conditions.

Air Temperature Control System in a Building on the Basis of Mathematical Modelling

In the article the authors solve a crucial objective of reducing the cost of heating services through the introduction of a system, controlling boilers and heating devices, based on modelling of the building and predicting heating systems functioning and operation. The authors describe the method of mathematical modelling of heating systems of the building and represent the developed mathematical models, pledged and installed into the developed automated system. The authors have offered an automated system of dispatch control of the boilers with the elements of computer simulation and modelling.

Spring Freeze Effect on Wheat Yield is Modulated by Winter Temperature Fluctuations: Evidence from Meta‐Analysis and Simulating Experiment

AbstractIncreasing climatic variability is projected to affect large‐scale atmospheric circulation, triggers and exacerbates more extreme weather events, including winter warming and more frequent extreme low temperatures in spring. Historical data from 1961–2000 indicate these temperature fluctuations may seriously affect grain yield of winter wheat crops. In this study, a field air temperature control system (FATC) was used to simulate the winter warming, spring cold and freezing events in the field experiment in 2010–2011 to explore their impacts on growth and yield of winter wheat. Eight elite wheat varieties released during 1961–2000 were included and four temperature scenarios were applied, including late spring freeze alone, winter warming + late spring freeze, early spring cold + late spring freeze and the normal temperature condition as control. Winter warming combined with late spring freeze significantly decreased tiller survival rate, leaf photosynthetic rate and leaf growth in wheat plants, and reduced the spike number and kernel number per spike, and the final grain yield. In contrast, the wheat plants experienced early spring cold had higher tiller survival rate, leaf photosynthetic capacity and sugar accumulation and improved tolerance to the late spring freeze, resulting in less yield loss, as compared with those without experiencing early spring cold. Both the meta‐analyses and the field experimental data demonstrated that the effects of later spring freeze stress on wheat yield were exacerbated by winter warming but were extenuated by early spring cold events. Therefore, it is important to consider the characteristics of temperature fluctuations during winter to spring for precise evaluation of climate change effects on wheat production.

Numerical modelling and experimental studies of thermal behaviour of building integrated thermal energy storage unit in a form of a ceiling panel

ObjectiveThe paper presents a new concept of building integrated thermal energy storage unit and novel mathematical and numerical models of its operation. This building element is made of gypsum based composite with microencapsulated PCM. The proposed heat storage unit has a form of a ceiling panel with internal channels and is, by assumption, incorporated in a ventilation system. Its task is to reduce daily variations of ambient air temperature through the absorption (and subsequent release) of heat in PCM, without additional consumption of energy. MethodsThe operation of the ceiling panel was investigated experimentally on a special set-up equipped with temperature sensors, air flow meter and air temperature control system. Mathematical and numerical models of heat transfer and fluid flow in the panel account for air flow in the panel as well as real thermal properties of the PCM composite, i.e.: thermal conductivity variation with temperature and hysteresis of enthalpy vs. temperature curves for heating and cooling. Proposed novel numerical simulator consists of two strongly coupled sub models: the first one – 1D – which deals with air flowing through the U-shaped channel and the second one – 3D – which deals with heat transfer in the body of the panel. ResultsSpatial and temporal air temperature variations, measured on the experimental set-up, were used to validate numerical model as well as to get knowledge of thermal performance of the panel operating in different conditions. ConclusionPreliminary results of experimental tests confirmed the ability of the proposed heat storage unit to effectively control the air temperature inside the building. However, detailed measurement of the temperature of PCM composite have shown some disadvantages of the panel used in the study, e.g. thickness of the walls and distribution of PCM should be optimized. This can be achieved with the aid of the numerical simulator developed in this research. Practical implicationsThe proposed ceiling panel, optimised from the point of view of thermal performance in a given environmental conditions, can be used as a part of ventilation systems in residential and office buildings.

Sensor and Actuator Fault Detection and Isolation for a High Performance Aircraft Engine Bleed Air Temperature Control System

In this brief, an unscented Kalman filter (UKF)-based method is developed to detect and isolate both temperature sensor and valve actuator faults of a high performance aircraft bleed air temperature control system . The proposed method involves two unscented Kalman filters: one is used to detect sensor fault and the other is dedicated to actuator fault detection. Nonlinear state space equations describing the engine bleed air temperature control system test rig dynamics are derived and utilized in the design and convergence analysis of the proposed fault detection and isolation method. Computer simulations and experiments have been conducted, and the proposed fault detection method is shown to be effective in detecting and isolating sensor and actuator faults.

Development of High Performance Aircraft Bleed Air Temperature Control System With Reduced Ram Air Usage

Conventional aircraft engine bleed air temperature regulation system is inefficient due to unnecessary ram air usage in cooling the bleed air, which in turn causes unnecessary drag and fuel consumption. This paper proposes an aircraft bleed air temperature control system, aiming at minimizing the ram air usage to reduce drag and fuel consumption while maintaining fast temperature control response. To achieve both of the objectives, a new control system configuration is developed to control both ram air and bypass flows in such a way that the bypass bleed air flow is automatically controlled at a small level that is just sufficient to maintain fast regulation of the flow temperature at the load. Analytical equations describing the system dynamics and linearized model are derived and utilized in the overall bleed air temperature control design and analysis. PI control and optimal output feedback are investigated. Computer simulations and experiments have been conducted, and the proposed control system is shown to be effective in reducing ram air usage and maintaining fast temperature control response in the meantime.

Individual and collective climate control in aircraft cabins

A new concept for aircraft cabin climatisation has been developed in which the seat is the main Indoor Air Quality (IAQ) and temperature control system for the passengers containing provisions for local supply and local exhaust of air. Direct supply of clean outside air in the breathing zone, through the headrest of the seat, yields a high ventilation efficiency enabling e.g. local humidification and, depending on disturbances of the cabin ventilation system, 57-96% shielding against contaminants from other passengers. Exhaust of 0-2dm³/s per seat involves a cooling load of 0-20 W, which is up to 20% of the metabolism of a seated person. Control of cabin temperature takes place at two levels: 1. individual control; the passenger influences his seat surface temperature by varying the exhaust flow; and 2. on cabin scale, the control is based on a 'voting' system based on the average individual exhaust flows.

Real-time tuning of PI controllers in HVAC systems

The problem of tuning single-loop controllers in heating, ventilating and air conditioning (HVAC) systems is explored. The HVAC process was described by a first-order-plus-dead-time (FOPDT) model. By using recursive least squares method, the model parameters were updated while the system remained in closed-loop. The H∞ loop-shaping tuning rules published in the literature were transformed to discrete-time tuning rules and were implemented in an adaptive PI control strategy. The methodology was applied to a discharge air temperature (DAT) control system. The output responses of adaptive PI controller were compared with a LQR optimal adaptive controller. Simulation results show that the adaptively tuned PI controller is able to track setpoint changes very well in the presence of changes in plant parameters, disturbances and external noise acting on the system. Copyright © 2004 John Wiley & Sons, Ltd.