Real-time Temperature Control Research Articles

Anti-freezing prediction model for different flow patterns of air-cooled heat exchanger

Water heat load may get lower than the huge cooling capacity of air for air-cooled heat exchanger in winter, resulting in the freezing risk of finned tube bundles, so the water temperature distribution inside the tube under various working conditions stands the premise issue for the security and energy efficiency of dry cooling system. Based on the energy balance and heat transfer analyses, the anti-freezing prediction model of air-cooled heat exchanger is developed and experimentally validated at different low ambient temperatures with the maximum deviation of 16%. Taking a six-row plate finned tube heat exchanger as the research object, the water temperature distribution in any tube and the critical anti-freezing parameters are obtained with different air/water flow patterns at various ambient temperatures, air face velocities, inlet water temperatures, and water flow rates. The results show that the finned tube bundle with slotted fins is superior to the flat fins in heat transfer performance, but faces more serious freezing risks in cold winter. In the baseline case, the average outlet water temperature of the slotted finned tube bundle decreases by 3.9 °C compared to the flat finned tube bundle. For the air/water cross-counter flow pattern, the critical freezing position is fixed and appears at the water exit of upwind row. While for the air/water cross-cocurrent flow, the minimum water temperature varies with operating conditions, but it always happens at the row 1 or row 4. The anti-freezing of air-cooled heat exchanger can be realized by reasonably matching the air/water heat capacity as well as transforming the air/water flow patterns. The proposed anti-freezing prediction model is of potential benefit to the real-time temperature distribution forecast, freezing analyses, and control strategies for air-cooled heat exchanger in winter.

RF-ICP Thermal Plasma for Thermoplastic Waste Pyrolysis Process with High Conversion Yield and Tar Elimination

This paper demonstrates an RF thermal plasma pyrolysis reaction apparatus that achieves 89 wt.% reaction conversion yield with no tar content. The demonstrated experimental apparatus consists of a 1100 W RFVII Inc. (104 Church St, Newfield, NJ 08344, United States) @ 13.56 MHz RF thermal plasma generator, a Navio matching network, intelligent feedback controller, and an 8-turn copper RF-ICP torch embedded in a 12 L thermochemical reactor. The intelligent feedback controller optimizes the thermal performance based on feedback signals from three online gas analyzers: CO, CO2 and NOx. The feedback controller output signal controls the RF thermal plasma torch current that provides real-time temperature control. The proposed reaction system achieves precise temperature profiles for both pyrolysis and gasification as well as increases end-product yield and eliminates undesired products such as tar and char. The identified hydrocarbon liquid mixture is 90 wt.% gasoline and 10 wt.%. diesel. The 8-turn RF-ICP thermal plasma torch has an average heating rate of +35 °C/min and a maximum operating temperature of 2000 °C and is able to sustain stable flame for more than 30 min. The reaction operating parameters are (550–990 °C τ = 30 min for pyrolysis and (1300 °C τ = 1 sec) for the gasification process. The identified hydrocarbon liquid products are 90 wt.% of a n-butyl-benzene (C6H5C4H9) and oluene (C7H8) mixture with less than 10 wt.% decane diesel fuel (C10 H22). Comsol simulation is used to assess the RF-ICP thermal plasma torch’s thermal performance.

Online reset strategy based on linear correlation for variable static pressure control of VAV system

In comparison with constant static pressure and total air volume control strategies, a static pressure reset strategy for variable static pressure control of Variable Air Volume (VAV) air conditioning systems shows evident energy-saving potential. How to establish a relationship between feedback parameters representing the load demand and duct static pressure setpoint has been attached great importance to. This study provides a novel static pressure reset strategy with a linear adjustment algorithm to build a simple linear functional relation between the terminal maximum damper position and the static pressure setpoint. Also, the robust regions are introduced into the algorithm to enhance the system stability and online applicability. Experiments are conducted to compare the proposed strategy with a fixed static pressure strategy and a static pressure reset strategy with a fixed step value in an integrated experimental control system for a VAV system. Experimental results indicate that all three strategies can realize real-time control of room temperature while the proposed strategy has better stability with the least number of setpoint reset times. The mean of the damper position is 16.74% and 8.56% higher than the other two strategies accompanying with a minimum of 5% energy saving of the proposed control method.

Multi-Building Systems Thermal and Energy Management via Geothermal Heat Pump

With the growing concern on energy consumption, optimization and control of Geothermal Heat Pump (GHP) systems have become a research hotspot, which can help solve the problem of building energy conservation and shortage. The superiority of current control schemes of GHP systems is often reflected on an individual building with a separate GHP system. However, with the development of urban construction and the increase of population density, study on the district/area case in built-up areas deserves more attention. This paper focuses on typical cases of one GHP system serving multiple buildings and the community-level coordination of GHP systems. In particular, we present a high-order thermal dynamic model of radiator pipes combined with a commonly used second-order resistance-capacitance model for radiator heating/cooling. We design controllers to improve the efficiency of heat pumps and the ability to track a given nominal point of electrical power consumption in a distributed way, without sacrificing too much user comfort. Simulation results show that the proposed real-time distributed temperature control schemes are effective.

A Temperature-Control System for Continuous-Flow Microwave Heating Using a Magnetron as Microwave Source

A real-time temperature control system is designed for microwave heating of a continuous-flow substance. In this system, a magnetron is used as the microwave source, and its output power can be continuously adjusted though circuit design. A programmable logic controller (PLC) is used to procedure the temperature and power data as well as lead the whole control decision. The sample temperature can be controlled by regulating the output power of the magnetron though the control signal from the PLC during the heating process. The complete system is finally assembled into a user-friendly device, where the users can operate and monitor the heating process conveniently though a touch screen. A temperature-dependent material (Phosphoric acid) is used in system tests. The results show that the designed system can successfully achieve the desired temperature with an acceptable accuracy and stability.

Development of Real-Time Software for Thomson Scattering Analysis at NSTX-U

The Thomson scattering (TS) diagnostic on the National Spherical Tokamak eXperiment Upgrade (NSTX-U) has been an essential system for many operational campaigns due to its function of measuring plasma electron density and temperature. Constructive feedback to improve the next plasma discharge, however, has been limited because of in-between shots analysis. Plasma control, therefore, desires a diagnostic system that is real-time capable. This contribution presents the development of software that demonstrates the feasibility of a real-time TS diagnostic system for NSTX-U. The developed software is able to evaluate the electron temperature and density within 2.5 ms.The overall system requirement is specified by a 60-Hz timing cycle, which is driven by the TS laser pulse rate. The real-time software processes the peak amplitudes of the detected photons, evaluates the electron temperature and density, and then outputs them to an analog output card that is used to interface with the NSTX-U control. The real-time software is implemented in an object-oriented architecture using C++11. C++11 software components include class, Atomic data types for synchronization, and a Hash data structure. The software application makes use of multiple threads that run concurrently: a thread to acquire the photon peak amplitude and feed a circular buffer, threads to evaluate the electron density and temperatures, and a thread that supplies corresponding output voltages and feeds the output card.In summary, the new real-time TS system has been proven to meet the 60-Hz system requirement. For this reason, the software implementation was deemed successful. In future NSTX-U campaigns, this diagnostic will be a great asset enabling real-time plasma density and temperature control.

Theoretical and experimental modeling of interstitial laser hyperthermia with surface cooling device using Nd3+-doped nanoparticles.

To improve methods of laser hyperthermia for the treatment of bulk malignant neoplasms, an urgent task is the development of techniques and devices that automatically control heating at a given tissue depth and ensure its uniformity. The article proposes the concept of a system for performing hyperthermia with real-time spectroscopic temperature control and surface cooling, which allows to record spectra of diffusely scattered radiation and fluorescent signal from various depths of biological tissues by the means of the variation of the angle and distance between the fiber source of laser radiation and the receiving fiber. Theoretical and experimental modeling of the spatial distribution of diffusely scattered radiation and temperature inside the tissue with a fiber optic device providing surface cooling of the irradiated tissue, and recording spectral information from a given depth in real time, is presented. Simulation of radiation propagation in biological tissues, depending on the distance between the source and the receiver and the angle of their tilt, was carried out using the Monte Carlo method. Modeling of the temperature distribution inside the tissues was carried out by means of a numerical solution of the heat conduction equation. Experimental modeling was carried out on phantoms of biological tissues simulating their scattering properties as well as accumulation of the investigated nanoparticles doped with Nd3+ ions. It was shown that inorganic nanoparticles doped with rare-earth Nd3+ ions can be used as temperature labels for feedback to the therapeutic laser. According to the results of the theoretical simulation, optimal configurations of the relative arrangement of the fibers were chosen, as well as the optimum surface cooling temperatures for the given power densities. The heating of the phantom of the neoplasm containing the investigated nanoparticles doped with Nd3+ ions by laser radiation with an 805-nm wavelength and power density of 1W/cm2 up to 42°C at a depth of 1cm while maintaining the surface temperature within the limits of the norm was demonstrated.

Sistem Pengendalian Suhu dan Kelembaban Kumbung Jamur Tiram secara Realtime Menggunakan Esp8266

Oyster Mushroom is one of the high-value consumption mushrooms. The development of mushroom experienced rapid growth marked by the increasing number of farmers breeding mushroom is directly proportional to number of mushroom food business. The process of mushroom cultivation in mushroom’s greenhouse depends on physical factors such as temperature, humidity, light, pH of planting medium, and air aeration. Watering activity is done if the condition and humidity of mushroom's greenhouse was dry, three times a day at the morning, afternoon and evening. If the conditions of temperature and humidity fluctuate in the current seasons, it is not enough to be sprayed. High temperature and humidity fluctuations disturbed harvest. The results of this research are realtime temperature and humidity control system, esp8266 12-F and DHT22 sensor to read humidity value that can do watering and keep humidity greenhouse. The best humidity limit is 65% and maximum is 80%. If the humidity condition reaches 65%, then esp8266 will activate the relay to turn on the DC pump machine and nozzle spray. If humidity reached 80%, then esp8266 will turn off the DC pump. 80% humidity limit setting to avoid mushrooms from getting too wet. Humidity conditions monitored with android smartphone in realtime.

LampPort: a handheld digital microfluidic device for loop-mediated isothermal amplification (LAMP).

A major goal in the development of point-of-care (POC) devices is to build them as portable to provide a rapid and effective determination for disease pathogens. In nucleic acid testing, an optical detection system used to monitor the product of nucleic acid amplification has always been a bulky accessory. In this work, we developed a handheld, automatic and detection system-free thermal digital microfluidic (DMF) device for DNA detection by loop-mediated isothermal amplification (LAMP). Droplet manipulation and real-time temperature control systems were integrated into a handheld device. The control software could be installed into any tablet and communicate with the device via Bluetooth. In the experimentation, we loaded 2-μl samples with an electrowetting force into sandwich-structured DMF chips, thereby considerably reducing reagent consumptions. After an on-chip LAMP reaction, we added a highly concentrated SYBR Green I droplet and mixed it with a reaction droplet to enable product detection with the naked eye. This step prevented aerosol contamination by avoiding the exposure of the reaction droplet to the air. Using a blood parasite Trypanosoma brucei as a model system, this system showed similar results as a commercial thermal cycler and could detect 40 copies per reaction of the DNA target. This low-cost, compact device removed the bulky optical system for DNA detection, thus enabling it to be well suited for POC testing.

Development of Drone Cargo Bay with Real-Time Temperature Control

In order to deliver medical products (medicines, vaccines, blood packs, etc.) in time for needed areas, a method of transporting goods using drones is being studied. However, temperature-sensitive medical products may decay due to outside temperature changes. The time required to transport over the distance may vary a lot as well. As a result, the likelihood of the goods deteriorating is very high. There is a need for a study on cargo bay to prevent this and to protect the medical goods. In this paper, in order to protect the temperature sensitive medical goods, the inside cargo bay is equipped with the cooling fan device and the electric heating elements. These elements can be monitored and controlled according to the user’s discretion. By using the web server built inside the cloud server, the temperature can be controlled in real-time from anywhere without the limitation of distance. We built the proposed device, and installed it on the drone cargo bay. The test results show that the cargo bay can be temperature-controlled, and the setting can be maintained over a great distance. The user can watch the temperature variations during the transport and ascertain the goodness of the medical supply with the data. It is expected that such development can greatly enhance the utility of the drone operations, especially for the medical supply transport applications.

Quality analysis of microwave dried iron yam chips controlled by infrared thermal imaging

Abstract The aim was to study the real-time temperature control by infrared thermography and the quality changes of the iron yam chips during drying processes. Microwave (MW) and heat pump (HP) were used to dry iron yam chips at 50, 60 and 70 °C. The material surface temperatures were online controlled by infrared thermal imaging system in the process of microwave drying. Temperature, drying efficiency, texture and color were estimated. The experimental results were shown on the basis of drying process characteristics and dried product qualities. Temperature fluctuations became more violent with the increase of drying time and drying temperature, and had a negative impact on the quality of dried iron yam chips. There were no significant differences of hardness and cohesiveness between both drying methods. The springiness and chewiness values of iron yams dried by HP were lower than samples dried by MW. It is worth noting that lightness and white index values of the iron yam chips dried by microwave at 70°C were obviously lower (p < 0.05) than the fresh samples and the iron yam chips dried by heat pump.

Automated Temperature Control with Adjusting Outlet Valve of Fuel in the Process of Cooking Palm Sugar

In this paper, a real-time temperature control system for coconut sugar cooking is presented. It is based on a thermocouple temperature sensor. The temperature in the closed evaporator is used as a control variable of the DC servo control system for opening and closing of a valve embedded in a gas burner. The output power level, which is necessary in order to reach the target temperature is controlled by the microcontroller ATMega328P. A circuit module for control of the valve and temperature sensors as well as software for data acquisition have been implemented. The test results show that the system properly stabilizes the temperature in the closed evaporator for coconut sugar cooking in the range from room temperature to 110°C. A set point can be reached and held with an accuracy of ±0.75°C at a temperature of 110°C for 60 minutes.

Printability Study of Bioprinted Tubular Structures Using Liquid Hydrogel Precursors in a Support Bath

Microextrusion-based bioprinting within a support bath material is an emerging additive manufacturing paradigm for complex three-dimensional (3D) tissue construct fabrication. Although a support bath medium enables arbitrary in-process geometries to be printed, a significant challenge lies in preserving the shape fidelity upon the extraction of the support bath material. Based on the bioprinting in a support bath paradigm, this paper advances quantitative analyses to systematically determine the printability of cell-laden liquid hydrogel precursors towards filament-based tissue constructs. First, a yield stress nanoclay material is judiciously selected as the support bath medium owing to its insensitivity to temperature and ionic variations that are considered in the context of the current gelatin-alginate bio-ink material formulation. Furthermore, phenomenological observations for the rheology-mediated print outcomes enable the compositions for the bio-ink material (10% gelatin, 3% alginate), in tandem with the support bath medium (4% nanoclay, 0.5% CaCl2), to be identified. To systematically evaluate the performance outcomes for bioprinting within a support bath, this paper advances an experimental parametric study to optimize the 3D structural shape fidelity by varying parameters such as the layer height, extrusion flowrate, printing temperature, and printhead speed, towards fabricating complex 3D structures with the stabilization of the desired shape outcome. Specifically, it is found that the layer height and printhead speed are determinant parameters for the extent of successive layer fusion. Moreover, maintenance of an optimal bath temperature is identified as a key parameter for establishing the printability for the hydrogel bio-ink. Studying this effect is enabled by the custom design of a PID temperature control system with integration with the bioprinter for real-time precision control of the support bath temperature. In order to qualify the printed construct, a surface irregularity metric, defined as the average height difference between consecutive local maximum and minimum points of the binary image contour for the printed structure, is advanced to evaluate the quality of the printed constructs. Complex one-to-four bifurcating tubular structure prints demonstrate the applicability of the optimized bioprinting parameter space to create exemplar 3D human vessel-like structures. Finally, a cell viability assay and perfusion test for a printed cell-laden tubular element demonstrates high cell survival rates and leakage-free flow, respectively.

Precise Control of Target Temperature Using N6-Cyclohexyladenosine and Real-Time Control of Surface Temperature.

Targeted temperature management is standard of care for cardiac arrest and is in clinical trials for stroke. N6-cyclohexyladenosine (CHA), an A1 adenosine receptor (A1AR) agonist, inhibits thermogenesis and induces onset of hibernation in hibernating species. Despite promising thermolytic efficacy of CHA, prior work has failed to achieve and maintain a prescribed target core body temperature (Tb) between 32°C and 34°C for 24 hours. We instrumented Sprague-Dawley rats (n = 19) with indwelling arterial and venous cannulae and a transmitter for monitoring Tb and ECG, then administered CHA via continuous IV infusion or intraperitoneal (IP) injection. In the first experiment (n = 11), we modulated ambient temperature and increased the dose of CHA in an attempt to manage Tb. In the second experiment (n = 8), we administered CHA (0.25 mg/[kg·h]) via continuous IV infusion and modulated cage surface temperature to control Tb. We rewarmed animals by increasing surface temperature at 1°C h-1 and discontinued CHA after Tb reached 36.5°C. Tb, brain temperature (Tbrain), heart rate, blood gas, and electrolytes were also monitored. Results show that titrating dose to adjust for individual variation in response to CHA led to tolerance and failed to manage a prescribed Tb. Starting with a dose (0.25 mg/[kg·h]) and modulating surface temperature to prevent overcooling proved to be an effective means to achieve and maintain Tb between 32°C and 34°C for 24 hours. Increasing surface temperature to 37°C during CHA administration brought Tb back to normothermic levels. All animals treated in this way rewarmed without incident. During the initiation of cooling, we observed bradycardia within 30 minutes of the start of IV infusion, transient hyperglycemia, and a mild hypercapnia; the latter normalized via metabolic compensation. In conclusion, we describe an intravenous delivery protocol for CHA at 0.25 mg/(kg·h) that, when coupled with conductive cooling, achieves and maintains a prescribed and consistent target Tb between 32°C and 34°C for 24 hours.

Microstructural characterization of Ni-based self-fluxing alloy after selective surface-engineering using diode laser

The microstructural characterization of thermal-sprayed Ni-based self-fluxing alloy (Metco-16C®) after laser-assisted homogenization treatment was performed. To this end, a high-power diode laser system was used. This supported the real-time control of the target homogenization temperature at the substrate surface. Non-homogeneities of the macrosegregation of certain elements (C and Cu) and the local concentration of Cr-based carbides and borides in certain regions in the as-sprayed state could be enhanced with the application of homogenization. After homogenization at 1423 K, the hardness of the thermal-sprayed layer was found to have increased by 1280 HV from the as-sprayed state (750 HV). At this homogenization temperature, the microstructure of the thermal-sprayed layer consisted of a lamellar structuring of the matrix phase (austenite and Ni3Si) with fine (<5 μm) carbides and borides (the rod-like phase of Cr5B3, the lumpy phase of M23C6, and the extra-fine phase of M7C3). Despite the formation of several kinds of carbides and borides during homogenization at 1473 K, the lowest hardness level was found to be less than that of the as-sprayed state, because of the liquid-state homogenization treatment without formation of lamellar structuring between austenite and Ni3Si.

A computer model for particle-like simulation in broiler houses

The behavior of chickens in broiler houses is affected by many conditions that involve, from the dimensions and design of the house, to the real-time control of temperature and humidity. A lot of experience is available which provides useful recommendations leading to reasonable efficiency of broiler houses. Trying different alternatives in practice is, or course, very expensive. For this reason, computer simulation becomes an extremely useful tool. Presently, standard computers make it possible to build and run simulation models in which each broiler is considered as a single “particle” whose behavior is subject to the interaction with other broilers and the environment. The objective of this paper is to introduce, discuss, and analyze a new computational model, that, to the best of our knowledge, is the first of this type. The model considers the displacements of the chickens as being analogous to the motion of physico-chemical particles (atoms or molecules), relying on Langevin dynamics and taking temperature, air speed, humidity, house dimensions, chicken population, availability of eaters, and water drinking systems into consideration. The parameters of our model were tunned both using extreme and standard assumptions on the behavior of chickens in a broiler house.

Multiloop Integral Controllability Analysis for Nonlinear Multiple-Input Single-Output Processes

Multi-loop integral control is still one of the most popular control strategies in industry due to its simplicity, efficiency, offset free tracking, and capability for fault tolerance. Skogestad and Morari introduced Decentralized Integral Controllability (DIC) to investigate the decentralized unconditional stability under multi-loop integral control for square systems. However, in engineering practice, some multivariable processes may not be square, which often utilize multiple redundant control inputs for the regulation of only one single output. This study extends the concept of Decentralized Integral Controllability to non-square systems, and presents sufficient conditions for Multiple-Input Single-Output nonlinear processes based on singular perturbation analysis. The proposed controllability analysis method is applied in the control of a real time temperature control system and achieves desired temperature tracking results.

Design of a Data Acquisition System in the Cooling Test for ITER Radial X-Ray Camera

The Radial X-ray camera (RXC) is a diagnostic for the ITER tokamak. During baking and operation of ITER, the detector environment temperature will be up to 240°C, whereas the detectors must be kept below 70°C. Therefore, cooling of the detectors mounted in the camera is critical and necessary. In order to verify the effect of gas cooling for RXC detectors, a relevant test has been designed. Since the outcome of this test will be the supply of the RXC cooling system, the ITER Instrument and Control strategy was selected. Therefore, a Data Acquisition (DAQ) system was developed based on the Experimental Physics and Industrial Control System (EPICS) framework, which implements functions for real-time data acquisition, temperature control, supervision, and archiving. Moreover, it is easy to configure control information according to user requirements. Also, some linear devices were used in the reconfiguration of EPICS. This technical note presents the entire architecture of the DAQ system and the details on the design of EPICS. The system has been implemented, and has provided reliable data for the experiment.

Feasibility of Real-Time Intraprocedural Temperature Control during Bone Metastasis Thermal Microwave Ablation: A Bicentric Retrospective Study

PurposeTo evaluate feasibility of using a thermocouple for temperature monitoring during microwave (MW) ablation of metastatic bone disease. Materials and MethodsThis retrospective study comprised 16 patients (8 men with mean age 63 y and 8 women with mean age 59 y) with 18 bone metastases treated with MW ablation using a thermocouple between March 2012 and October 2015. The mean maximum tumor size was 29.5 mm. MW ablation power was set between 15 W and 40 W and applied for 1–6 minutes. Thermocouple placements were as follows: epidural space (n = 7 cases), nerve roots (n = 9 cases), pleura (n = 1), and pericardium (n = 1). The procedure was considered technically successful when the MW and the thermocouple probes were accurately placed and thermoablation was initiated. Clinical success was defined as a 50% visual analog scale score decrease at 1 month as assessed by the operators. ResultsMean MW ablation time was 4.3 minutes with a mean energy of 30 W. Procedural success was 100%. In 16 cases with neural structure monitoring, temperature did not increase > 43°C. In 8 cases, MW ablation had to be discontinued because of temperature reaching 42°C. Efficacy of the procedure in regard to pain was achieved in 17 of 18 ablation sessions at 1 month. ConclusionsUse of a thermocouple during bone MW ablation is a feasible technique and may be a potentially useful tool to help avoid nontarget ablation surrounding tumors.

Photonic Packaging: Transforming Silicon Photonic Integrated Circuits into Photonic Devices

Dedicated multi-project wafer (MPW) runs for photonic integrated circuits (PICs) from Si foundries mean that researchers and small-to-medium enterprises (SMEs) can now afford to design and fabricate Si photonic chips. While these bare Si-PICs are adequate for testing new device and circuit designs on a probe-station, they cannot be developed into prototype devices, or tested outside of the laboratory, without first packaging them into a durable module. Photonic packaging of PICs is significantly more challenging, and currently orders of magnitude more expensive, than electronic packaging, because it calls for robust micron-level alignment of optical components, precise real-time temperature control, and often a high degree of vertical and horizontal electrical integration. Photonic packaging is perhaps the most significant bottleneck in the development of commercially relevant integrated photonic devices. This article describes how the key optical, electrical, and thermal requirements of Si-PIC packaging can be met, and what further progress is needed before industrial scale-up can be achieved.