Temperature-based Control Research Articles

An intelligent thermal comfort control strategy for air conditioning of fuel cell vehicles

Thermal comfort is an important indicator for evaluating vehicle air conditioning, with many influencing factors, but traditional vehicle air conditioning control only take temperature as the control target, neglecting the passenger's actual thermal comfort situation, which cannot automatically adapt to the thermal comfort needs of different passengers. To address this issue, this paper establishes an air conditioning model based on a fuel cell vehicle (FCV) and proposes a control strategy based on thermal comfort, using deep reinforcement learning based on PPO algorithm to establish the control model. Which can automatically control the compressor and blower, this paper conducts simulation analysis under four different environmental conditions which including static and dynamic situations. The results show that when using the intelligent thermal comfort control strategy, the overall thermal sensation values of passengers are 0.006, 0.005, 0.033, and 0.102, respectively; which are 0.088, 0.333, 0.093, and 0.120 lower than the temperature-based control strategy, this proves that the control strategy proposed in this paper can achieve better thermal comfort for passengers.

Applicability evaluation of a temperature humidity index-controlled ventilation system in livestock using a building energy simulation model

In general, for livestock building, a simple system for controlling the HVAC system that is based only on the indoor air temperature is applied. This study evaluated the applicability of temperature humidity index (THI)-based ventilation systems installed in livestock buildings using a building energy simulation model. Based on the monitoring data of an actual pig house, the integrated predictive performance of the indoor temperature and humidity of the building energy simulation model was calibrated. Additionally, the indoor environment of the existing temperature-based control and THI-controlled ventilation systems was compared through simulations. The average THI and the section exceeding the THI threshold were both lower compared to the existing system. This was because the part load ratio of the fans of the THI-controlled ventilation system was higher than that of the existing system, indicating better ventilation. These results suggest that THI-based ventilation systems can overcome the limitations of existing temperature-based systems and effectively improve the thermal stress management of livestock buildings. This study portrays that the indoor environment can be improved by simply changing control variables, while presenting the field applicability and research value of THI-based control systems in the management of livestock environments.

Potential Cooling Energy Savings of Economizer Control and Artificial-Neural-Network-Based Air-Handling Unit Discharge Air Temperature Control for Commercial Building

Heating, ventilation, and air-conditioning (HVAC) systems play a significant role in building energy consumption, accounting for around 50% of total energy usage. As a result, it is essential to explore ways to conserve energy and improve HVAC system efficiency. One such solution is the use of economizer controls, which can reduce cooling energy consumption by using the free-cooling effect. However, there are various types of economizer controls available, and their effectiveness may vary depending on the specific climate conditions. To investigate the cooling energy-saving potential of economizer controls, this study employs a dry-bulb temperature-based economizer control approach. The dry-bulb temperature-based control strategy uses the outdoor air temperature as an indicator of whether free cooling can be used instead of mechanical cooling. This study also introduces an artificial neural network (ANN) prediction model to optimize the control of the HVAC system, which can lead to additional cooling energy savings. To develop the ANN prediction model, the EnergyPlus program is used for simulation modeling, and the Python programming language is employed for model development. The results show that implementing a temperature-based economizer control strategy can lead to a reduction of 7.6% in annual cooling energy consumption. Moreover, by employing an ANN-based optimal control of discharge air temperature in air-handling units, an additional 22.1% of cooling energy savings can be achieved. In conclusion, the findings of this study demonstrate that the implementation of economizer controls, especially the dry-bulb temperature-based approach, can be an effective strategy for reducing cooling energy consumption in HVAC systems. Additionally, using ANN prediction models to optimize HVAC system controls can further increase energy savings, resulting in improved energy efficiency and reduced operating costs.

Modeling and demand-based control of responsive building envelope with integrated thermal mass and active thermal insulations

The static nature of current envelope design and operation is diametric to the mutable and transient forces and energies acting on our building stocks. Responsive building envelopes (or RBEs) have shown substantial energy saving potential for buildings by adaptively providing passive cooling/heating. In this research, an easy-to-implement yet flexible ‘demand-based’ control rule is proposed based on demand analysis to optimally control RBEs that integrate active insulation systems (AISs) and a sensible thermal energy storage (TES) layer. The controller developed herein calculates the desired thermal resistance for AIS layers and provides on-demand control of the heat flow into and out of the thermal mass to reduce AC load. It provides several benefits over the simple temperature-based controllers while does not require the complex formulation as needed for model predictive control. To quantify the thermal behavior and energy performance, a thermal network model is developed for RBEs to perform wholebuilding energy simulations of a residential thermal zone in six representative cities in the US. The results show apparent benefits of demand-based control strategy over traditional temperature-based control by offering higher energy savings and LPD reduction, especially in mild climate zones and during transitional seasons. Some design and implementation considerations for REBs with integrated AISs and TES are also discussed.

Feedback-controlled laser ablation for cancer treatment: comparison of On-Off and PID control strategies.

Laser ablation is a rising technique used to induce a localized temperature increment for tumor ablation. The outcomes of the therapy depend on the tissue thermal history. Monitoring devices help to assess the tissue thermal response, and their combination with a control strategy can be used to promptly address unexpected temperature changes and thus reduce unwanted thermal effects. In this application, numerical simulations can drive the selection of the laser control settings (i.e., laser power and gain parameters) and allow evaluating the thermal effects of the control strategies. In this study, the influence of different control strategies (On-Off and PID-based controls) is quantified considering the treatment time and the thermal effect on the tissue. Finite element model-based simulations were implemented to model the laser-tissue interaction, the heat-transfer, and the consequent thermal damage in liver tissue with tumor. The laser power was modulated based on the temperature feedback provided within the tumor safety margin. Results show that the chosen control strategy does not have a major influence on the extent of thermal damage but on the treatment duration; the percentage of necrosis within the tumor domain is 100% with both strategies, while the treatment duration is 630 s and 786 s for On-Off and PID, respectively. The choice of the control strategy is a trade-off between treatment duration and unwanted temperature overshoot during closed-loop laser ablation. Clinical Relevance-This work establishes that different temperature-based control of the laser ablation procedure does not have a major influence on the extent of thermal damage but on the duration of treatment.

Experimental analysis of fiber-reinforced laminated composite plates with embedded SMA wire actuators

Shape memory alloy (SMA) wires are effective smart actuators since they provide relatively large actuation force and strain in a very limited space. Embedding SMA wires in flexible laminated composite plates or shells allows for creating active structures for morphing applications. However, the design of such structures is challenging due to the nonlinear thermomechanical coupling of SMA materials, the adhesion of the SMA actuators to the resin, the effect of temperature on the adhesion strength, the heat transfer between the SMA wires and the surrounding laminate, and the convection boundary conditions. This paper presents an experimental analysis of smart fiber-reinforced composite laminated plates with embedded SMA wires, focusing on the relationship between the applied electric current, measured temperature of the SMA wires, and the resulting tip deflection. A temperature-based control method was developed to achieve the required wire temperature and tip deflection as quickly as possible. Results showed that the fiber-orientation angle of the composite plies and the convection boundary conditions have significant effects on the structure’s actuation. With cyclic actuation, damage starts around the heated SMA wires and can grow to cause delamination at areas between neighboring SMA wires and yielding of the matrix material, resulting in permanent deformation.

Investigation of energy savings potential of multi-variable differential temperature control in economizer

• This study proposed multi-variable temperature-based controls for economizers. • The proposed controls additionally considered latent loads in the typical temperature-based methods. • The results showed the substantial savings potential of system cooling loads in the proposed controls. In commercial buildings, building mechanical systems use over 33–50% of the total building energy consumption. As an energy conservation measure, an economizer can be used to reduce energy consumption and operating costs by introducing cold outdoor air into building space based on the outside air temperature or enthalpy. Among control types of economizer, enthalpy-based control is the more energy-efficient approach for the economizer cycle in Korea. However, in reality, humidity sensors are often out of order in buildings, which disables enthalpy-based controls in economizers. Therefore, as a practical substitute, multi-variable temperature-based control was investigated in this study using the local outdoor air humidity to consider latent loads in the typical temperature-based control and supplement the frequent failures of humidity sensors. The results showed the substantial energy savings potential in temperature-based control, which is driven by reduced system loads in cooling coils in a mixed-humid climate. Also, an analysis of the psychrometric charts represented that the impact of multi-variable temperature-based control would be more significant in humid climates than dry or marine regions. The proposed approach can complement the conventional differential dry-bulb temperature control method and provide a guide for improved economizer operations to achieve better energy performance in hot and humid climates.

Experimental investigation on the effects of phase change material and different ventilation modes on the thermal storage, space heating and energy consumption characteristics of ventilated mortar blocks

Radiant heating floor integrated with micro encapsulated phase change material (PCM) can significantly increase the thermal storage capacity, and inside air channels can enhance the heat release flexibility. In this study, the impacts of micro encapsulated phase change material and ventilation on the thermal and energy characteristics of mortar blocks were experimentally investigated by a scaled system. Several mortar blocks with different amount of PCM were made, and the space heating performance and heating energy consumption were measured and analyzed under the same temperature-based control strategy. It is found out that when the mass ratio of PCM is 8.7%, the required heating time is increased by 78.5% and the thermal storage capacity is increased by 80.3% as compared to pure mortar block. Ventilation can further increase the energy consumption by more than 22.7%. Besides, by shifting the ventilation mode, the space heating and cooling rate can be flexibly adjusted, which is essential for the flexible operation of the new heating system. The concern of the maximum and reasonable weight percentage of the micro encapsulated PCM is also proposed and discussed.

Analysis of the integration of the three-way catalyst thermal management in the on-line supervisory control strategy of a gasoline full hybrid vehicle

Full hybrid electric vehicles have proven to be a midterm viable solution to fulfil stricter regulations, such as those regarding carbon dioxide abatement. Although fuel economy directly benefits from hybridization, the use of the electric machine for propulsion may hinder an appropriate warming of the aftertreatment system, whose temperature is directly related to the emissions conversion efficiency. The present work evaluates the efficacy of a supervisory energy management strategy based on Equivalent Minimization Consumption Strategy (ECMS) which incorporates a temperature-based control for the thermal management of the Three-Way Catalyst (TWC). The impact of using only the midspan temperature of TWC is compared against the case where temperature at three different sampling points along the TWC length are used. Moreover, a penalty term based on TWC temperature has been introduced in the cost functional of the ECMS to allow the control of the TWC temperature operating window. In fact, beyond a certain threshold, the increase of the engine load, requested to speed up TWC warming, does not translate into a better catalyst efficiency, because the TWC gets close to its highest conversion rate. A gasoline P2 parallel full hybrid powertrain has been considered as test case. Results show that the effects of the different calibrations strategies are negligible on the TWC thermal management, as they do not provide any improvements in the fuel economy nor in the emissions abatement of the hybrid powertrain. This effect can be explained by the fact that the charge sustaining condition has a greater weight on the energy management strategy than the effects deriving from the addition of the soft constraints to control the TWC thermal management. These results hence encourage the use of simple setups to deal with the control of the TWC in supervisory control strategies for full hybrid electric vehicles.

Cyst-forming dinoflagellates in a warming climate

Many phytoplankton species, including many harmful algal bloom (HAB) species, survive long periods between blooms through formation of benthic resting stages. Because they are crucial to the persistence of these species and the initiation of new blooms, the physiology of benthic stages must be considered to accurately predict responses to climate warming and associated environmental changes. The benthic stages of dinoflagellates, called resting cysts, germinate in response to the combination of favorable temperature, oxygen-availability, and release from dormancy. The latter is a mechanism that prevents germination even when oxygen and temperature conditions are favorable. Here, evidence of temperature-mediated control of dormancy duration from the dinoflagellates Alexandrium catenella and Pyrodinium bahamense—two HAB species that cause paralytic shellfish poisoning (PSP)—is reviewed and presented alongside new evidence of complementary, temperature-based control of cyst quiescence (the state in which cysts germinate on exposure to favorable conditions). Interaction of the two temperature-based mechanisms with climate is explored through a simple model parameterized using results from recent experiments with A. catenella. Simulations demonstrate the importance of seasonal temperature cycles for the synchronization of cysts’ release from dormancy and are consistent with biogeography-based inferences that A. catenella is more tolerant of warming in habitats that experience a larger range of seasonal temperature variation (i.e., have higher temperature seasonality). Temperature seasonality is much greater in shallow, long-residence time habitats than in deep, open-water ones. As warming shifts species’ ranges, cyst beds may persist longer in more seasonally variable, shallow inshore habitats than in deep offshore ones, promoting HABs that are more localized and commence earlier each year. Recent field investigations of A. catenella also point to the importance of new cyst formation as a factor triggering bloom termination through mass sexual induction. In areas where temperature seasonality restricts the flux of new swimming cells (germlings) to narrow temporal windows, warming is unlikely to promote longer and more intense HAB impacts—even when water column conditions would otherwise promote prolonged bloom development. Many species likely have a strong drive to sexually differentiate and produce new cysts once concentrations reach levels that are conducive to new cyst formation. This phenomenon can impose a limit to bloom intensification and suggests an important role for cyst bed quiescence in determining the duration of HAB risk periods.

Simulations of a novel demand-controlled room-based ventilation system for renovated apartments

The study simulated and assessed a novel control algorithm for an innovative room-based ventilation system for renovated apartments. The novel system is a manifold of fans that connects to an air-handling unit to control the supply of airflow to each room in an apartment. The exhaust side has a 3-way damper to control the division of extract airflows. The simulation required demand-control of ventilation airflows in each room. This included CO2- and temperature-based control of supply to dry rooms and humidity- and temperature-based control of exhaust from wet rooms. The object-oriented software IDA-ICE includes a graphical interface for assembling the controls, which enabled custom simulations. The controls efficiently maintained sufficient air quality in each room and ensured balance of supply and exhaust. The room-based demand-controlled ventilation system achieved 74% savings in fan energy consumption relative to the reference constant air-volume system. The simulations indicated the need for less-resisting overflow vents in doorways to prevent infiltration heat loss when supplying bedrooms with greater airflow. Infiltration heat losses increased by 18% with closed doors despite the use of acoustic vents to assist overflow. Future measurements will aim to validate the demand-control algorithm and the performance of the novel system in real apartments.

On controllability of a fully thermally coupled four-product dividing wall column

Although potential for reduction of energy requirement and related carbon dioxide emissions is highly attractive – around 50% compared to conventional three column sequences – process industries are still reluctant to consider implementation of fully thermally coupled four products dividing wall columns, mainly due to concerns related to controllability of two or three vapour splits as encountered in complex DWC arrangements. This paper presents results of a simulation study that could bring some relief in this respect, indicating that a temperature-based control structure, in conjunction with tight control of temperature profiles in prefractionation section, as well as in the product draw regions of the column, is capable of restoring the operation to health from typical disturbances in feed quality and quantity. Combining temperature-based control with two composition controllers enables the column to be operated within finer margins, resulting in minimal over-purification and overall energy requirement.

Phase-change switching in 2D via soft interactions.

We present a new type of phase-change behavior relevant for information storage applications, that can be observed in 2D systems with cluster-forming ability. The temperature-based control of the ordering in 2D particle systems depends on the existence of a crystal-to-glass transition. We perform molecular dynamics simulations of models with soft interactions, demonstrating that the crystalline and amorphous structures can be easily tuned by heat pulses. The physical mechanism responsible for this behavior is a self-assembled polydispersity, that depends on the cluster-forming ability of the interactions. Therefore, the range of real materials that can perform such a transition is very wide in nature, ranging from colloidal suspensions to vortex matter. The state of the art in soft matter experimental setups, controlling interactions, polydispersity and dimensionality, makes it a very fertile ground for practical applications.

Temperature-Controllable Hydrogels in Double-Walled Microtube Structure Prepared by Using a Triple Channel Microfluidic System.

Hydrogels in the shape of double-walled microtubes possess great potential for development into artificial human blood vessels. In this work, we have prepared temperature-responsive tubular hydrogels with selectively controllable wall diameters, by using alginate templated photopolymerization in a triple channel microfluidic device. These tubular hydrogels mimic human blood vessels because of the separate thermally active inner and passive outer walls. The different behavior of each wall leads to the expansion of the hollow center volume with increasing temperature. This temperature-based control of the hollow center volume cannot be achieved in the case of conventional hydrogel microtubes. Furthermore, through this method, the hydrogels can be modified to achieve a controllable outer diameter while maintaining the hollow center dimensions simply by changing the position of the hydrogel walls. The ability to change the layer properties of the developed system indicates that the preparation of hydrogels with various monomers is possible.

Influence of rearing-water temperature on life stages\u2019 vector attributes, distribution and utilisation of metabolic reserves in Culex quinquefasciatus (Diptera: Culicidae): implications for disease transmission and vector control

BackgroundThis study aims at determining the effects of rearing water temperature on immature development, adult vectorial attributes and teneral accumulation in Culex quinquefasciatus (Cx. quinquefasciatus) mosquitoes. Immature life stages of the species were reared (to adulthood) in water media with temperature regimens of 28, 30, 32 and 34 °C generated and maintained by digital electrical thermostats. Immature and adult vectorial attributes (i.e. duration of development, growth rates, immature and adult survivorship, emergence rates and adult longevity), and rates of accumulation, distribution and utilisation (for pupation and eclosion) of teneral reserve (lipid, glucose, glycogen and protein) by life stages of the species were determined.ResultResults revealed significant negative effects of temperature increase on all parameters measured. Among these, only rate of larval growth (range = 0.0589 ± 0.0017 to 0.0930 ± 0.0003 mg/day) increased with temperature rise; others reduced with rise in temperature. Total immature duration (9.75 ± 0.09 to 6.43 ± 0.11 days), immature survivorship (94.01 ± 0.18 to 73.26 ± 3.72%), total emergent adults (72.00 ± 2.14 to 14.50 ± 2.67 adults/100 larvae), percentage of emergence, adult daily survivorship (76.86 ± 1.87 to 63.66 ± 0.18%) and post-emergence longevity (23.91 ± 2.97 to 16.90 ± 1.97 days) reduced with increase in temperature. Accumulation of teneral components increased across larval instars, but decreased with temperature rise and at metamorphosis (pupation and eclosion). Immature composition for lipid, glucose, glycogen and protein ranged, respectively, from 9.79 ± 1.05 to 20.07 ± 0.33, 8.49 ± 0.44 to 14.33 ± 0.44, 28.19 ± 2.34 to 42.87 ± 0.12 and 24.11 ± 0.71 to 35.55 ± 0.15 μg/mosquito. While, adult values for these ranged from 7.53 ± 0.40 to 20.66 ± 0.61, 7.45 ± 0.87 to 13.86 ± 0.83, 22.63 ± 0.85 to 33.64 ± 0.79, and 17.81 ± 1.02 to 31.45 ± 1.40 μg/mosquito, respectively. Glycogen and protein had the highest rates of accumulation, while metabolic reserves utilised for pupation and eclosion varied significantly with temperature change.ConclusionThis study revealed significant effects of temperature on the entomological parameters measured. Vectorial fitness indices, such as duration of immature development and survivorship, emergence rates, adult survivorship and longevity, and teneral accumulation and utilisation, tend to reduce with increase in temperature, while larval growth rates increased with temperature rise. The information generated is vital for developing temperature-based models and life-stage control strategies.

A wet-bulb temperature-based control method for controlling the heat balance of the ground soil of a hybrid ground-source heat pump system

Hybrid ground-source heat pump system has been widely used for mitigating the heat accumulation problem of conventional ground-source heat pump systems. This article proposes a wet-bulb temperature...

Development of a Wet-bulb Temperature-based Heat Balance Control Method for a Hybrid Ground Source Heat Pump System

Hybrid Ground Source Heat Pump (HGSHP) system has been widely used for mitigating the heat accumulation problem of conventional GSHP systems. This paper proposes a wet-bulb temperature-based control method for a HGSHP system which comprises a GSHP and a conventional water-cooled chiller (WCC) by using a cooling tower. With this method, the operation priority between the GSHP and the water-cooled chiller is determined according to the outdoor web-bulb temperature. A TRNSYS platform of the system is developed and simulations are carried out to investigate the system performance under the proposed control method. Meanwhile, simulations with two other control methods (reference methods), i.e., the GSHP-prioritized method and WCC-prioritized method, are also conducted. The study results show that the proposed control method has obvious advantage in controlling the heat balance of the ground source heat exchangers, and at the meantime no more energy is consumed when compared with the two reference control methods.

Burning Nettle (Urtica urens) Germination and Seedbank Characteristics in Coastal California

Burning nettle is a noxious weed that commonly infests coastal California vegetable fields. Weed control programs for lettuce and fresh spinach grown in this area do not adequately control burning nettle, and escaped weeds that mature are highly problematic during hand weeding and harvesting. Information on the biology and ecology of burning nettle is limited, and work was conducted to develop information about this weed. The objectives of this study were to evaluate the effect of temperature on burning nettle germination and to determine its base temperature value, to characterize the germination pattern of this weed and seedbanks under local California coastal conditions, and to estimate the optimal timing for burning nettle removal by herbicides and physical methods. The upper optimal temperature for burning nettle germination was 22.8 C, but there was no difference in the final germination percentage between 4 and 22.8 C. The base temperature was determined to be 3 6 0.2 C, and this information allowed the development of temperature-based optimal control timing models. In the field, burning nettle emerged throughout the year without any seasonal pattern, and germinable seeds were also found in the seedbank throughout the year. Burning nettle was able to complete a growth cycle throughout the year in coastal California. Burning nettle has a short growth cycle that allows it to set viable seeds within 466 6 13 growing degree days (GDD), and this timing is critical for burning nettle removal by herbicides, cultivation, or hand weeding. The optimal timing for phenmedipham application at 180 g ai ha–1was estimated to be 205 GDD. The germination and seedbank field studies indicate why burning nettle is so well adapted to the mild climate of coastal California. However, results presented here suggest strategies to reduce the burning nettle seedbank, improve its control, and allow more efficient lettuce and fresh spinach production.

Cold tolerance of third-instar Drosophila suzukii larvae

Drosophila suzukii is an emerging global pest of soft fruit; although it likely overwinters as an adult, larval cold tolerance is important both for determining performance during spring and autumn, and for the development of temperature-based control methods aimed at larvae. We examined the low temperature biology of third instar feeding and wandering larvae in and out of food. We induced phenotypic plasticity of thermal biology by rearing under short days and fluctuating temperatures (5.5–19°C). Rearing under fluctuating temperatures led to much slower development (42.1days egg-adult) compared to control conditions (constant 21.5°C; 15.7days), and yielded larger adults of both sexes. D. suzukii larvae were chill-susceptible, being killed by low temperatures not associated with freezing, and freezing survival was not improved when ice formation was inoculated externally via food or silver iodide. Feeding larvae were more cold tolerant than wandering larvae, especially after rearing under fluctuating temperatures, and rearing under fluctuating temperatures improved survival of prolonged cold (0°C) to beyond 72h in both larval stages. There was no evidence that acute cold tolerance could be improved by rapid cold-hardening. We conclude that D. suzukii has the capacity to develop at low temperatures under fluctuating temperatures, but that they have limited cold tolerance. However, phenotypic plasticity of prolonged cold tolerance must be taken into account when developing low temperature treatments for sanitation of this species.

Integrated numerical and experimental methodology for thermal-energy analysis and optimization of heritage museum buildings

Research effort was dedicated to the analysis of museums microclimate for the preservation of artifacts and indoor environment. In this paper, continuous monitoring and dynamic simulation of an ancient exhibition site are carried out to evaluate indoor microclimate and energy performance. The aim is to develop a multidisciplinary methodology for preserving artworks and historic buildings in the view of sustainability and comfort. The paper also shows how the environmental conditions of two thermal zones different for geometry, occupancy, ventilation rate, and heating, ventilation, and air conditioning (HVAC) systems are far from the values suggested by the regulations for the preservation of artifacts and from human comfortable set points of temperature and relative humidity. This work highlights the need for further investigation of historical exposition sites to reduce artworks' damaging and occupants' environmental stress. Practical application: Many historical buildings in European countries host exhibition sites. Indoor microclimate of such areas is often inappropriate for visitors' comfort, for artworks', and building preservation. In fact, usually HVAC systems operate according to simple temperature-based control protocols. This study shows how old architectures could present indoor environmental conditions far from the target, for artworks' preservation, for occupants' comfort, and for the building maintenance. This paper presents a numerical–experimental methodology applied to an architectural heritage. The analysis gives insight on this issue, and could guide building operators and service management to investigate and optimize indoor environmental conditions where artworks are preserved.