Effect Of Temperature Control Research Articles

Active phase and amplitude temperature control method for cryostat: A case in the thermodynamic temperature international comparison system

Achieving highly stable temperature control is essential for cryostats. However, the cryocooler used in cryostats, such as the pulse tube cryocooler, produces regular sinusoidal temperature fluctuations due to its inherent working principles. To establish a highly stable temperature environment, an active phase and amplitude control method for suppressing temperature fluctuation is proposed in this paper, by which the optimal phase and amplitude can be predicted in theory. To validate this approach, a thermal response model was developed based on experiments conducted in the thermodynamic temperature international comparison cryostat at approximately 3.7 K. Based on this model, we conducted both single-stage and multi-stage active temperature control experiments. The results demonstrate that the temperature control effect is the best when the active temperature control current is added at the second cold head, the fluctuation of the comparison copper block from 3.3mK to 0.166mK with 94.9 % suppression rate. The multi-stage joint temperature control reduced the temperature fluctuation with an attenuation rate of 95.4 %. These findings offer significant potential for improving temperature stability in future thermodynamic temperature comparison experiments.

A comparative performance study of terminal control strategy for the multi-split backplane cooling system in data centers

Multi-split backplane cooling, a typical rack-level cooling technology, has the advantage of solving local hot-spot problems with huge energy-saving potential. These systems adopt the multi-split mode, and the operation effect is affected by terminal control performance. However, there are factors in the operation process, such as superheat degree (SH), rack airflow, evaporating/condensing pressures, etc., which improve the control complication, particularly under large head load differences among different terminals. Therefore, appreciative control strategies for outlet air temperatures of terminal evaporators, including single-loop control limited by minimum stable superheat degree (SLC) and fan/electronic expansion valve (EEV) double-loop control (DLC), are proposed considering that cooling performance can be affected by both refrigerant flow and airflow. Then, comparative simulation studies are carried out to evaluate energy efficiency, control effect, and feasibility under the condition of different server heat distribution characteristics. Results indicate that the DLC strategy achieves 23% higher energy efficiency than the SLC strategy with a better temperature control effect when the inlet air temperature (IAT) difference between terminal evaporators is within ±5K. The SLC strategy has better reliability by more stable control of SH at IATs below 42°C, but it may lead to cooling failure when IATs exceed 42°C. An insufficient liquid supply problem may happen to the evaporator adopting the DLC strategy when the IAT is too high, which can be solved by adjusting the pressure differential between the evaporator and condenser. Moreover, the DLC system exhibits intense coupling effects, and how to decouple it is worthy of further study.

Study on the thermo-mechanical properties of adaptive thermal control anchoring materials in high-geothermal tunnels

The heat conduction of the rock in high-geothermal tunnels can damage the grout during the initial hardening process, which directly affects the effectiveness of the anchoring support of the surrounding rock. This paper proposed the incorporation of phase change materials in grout to provide the new modified grouting material with the ability to control temperature by exploiting the phase change absorption and exothermic properties of the material. The changes in thermomechanical parameters of anchoring grout containing microencapsulated phase change material (m-PCM) under high geothermal environment were investigated. The influences of m-PCM content on the temperature control effect and mechanical properties of modified grout under different high geothermal environments were explored through macro-mechanical, micro-structural, and thermo-physical property tests on the specimens. The results indicated that m-PCM can effectively control the early hydration temperature of the grout in a high temperature environment, which can slow down the rate of change of the hydration temperature and reduce the peak temperature. The temperature control performance of modified grouts improved as the phase-change content increased, but the mechanical properties showed a significant decline after the initial increase. The results of the scanning electron microscope (SEM) analysis indicated that the high curing temperature had a negative impact on the internal structural integrity of the grout. The addition of a small amount of m-PCM reduced the fractal dimension and irregularity of the pore space in the grouting material, ultimately improving the strength of the grout body. The addition of a certain amount of m-PCM could significantly reduce the thermal conductivity of the grout, with the thermal conductivity of the specimens decreasing as the temperature increased. These study results provided valuable experimental data and theoretical support for the design of cement-based grouting materials in high-geothermal tunnels.

Thermal performance analysis of lightweight phase change envelopes

To improve indoor thermal comfort and achieve building energy saving, a new envelope structure based on phase change material (PCM) was proposed. Firstly, an experimental platform was built around the room model, and the effects of ambient temperatures and PCM layout on the room temperature at different times were explored. Subsequently, a room numerical model heat transfer was constructed and the experimental verification was completed. The effects of PCM thickness, position, arrangement, and melting point difference on the room temperature at each time were analyzed based on the latent heat utilization rate, temperature fluctuation amplitude, and delay time. The experimental results show that when the walls all around the room contain PCM, the maximum indoor temperature can drop to 29.5 °C, and the maximum temperature drop is 3.2 °C. In addition, the greater the heat flow, the less effective the PCM is at controlling the temperature in the room. The simulation results show that when the PCM with a thickness of 15 mm is placed on the interior side of the wall, the maximum indoor temperature can be reduced to 29 °C, the maximum temperature drop is 2.9 °C, and the peak indoor temperature is extended by 0.8 h. When the PCM is arranged in series and the melting point difference is 3 K, the temperature control effect is the best, the maximum indoor temperature can be reduced to 25.7 °C, the maximum temperature drop is 2.9 °C, and the temperature fluctuation is the minimum, 2.6 °C.

An Alternative Reinforcement Learning (ARL) control strategy for data center air-cooled HVAC systems

Energy efficiency of data center is of great concern globally due to their large amount of energy consumption and the foreseeable growth in the demand of digital services in the future. Advanced control strategies are needed to reduce energy consumption. However, the optimization of data center HVAC control is a challenge task due to the complexity of the thermal dynamic models of buildings and uncertainties associated with both server loads and outdoor temperature. In this paper, we propose a new control strategy called Alternately-Reinforcement Learning-control(ARL), which realizes the alternating control of RL and proportional, integral and derivative (PID) for optimizing the control of air-cooled HVAC systems in data centers. The control object of the ARL is the speed set of the compressor and the condensing fan, and the control goal is to minimize energy consumption while maintaining temperature stability. The applied RL algorithm is Deep deterministic policy gradient (DDPG) and Proximal policy optimization (PPO). We pre-train the ARL strategy in offline environment firstly and deploy it in real data center environment for online testing. The test results show that the ARL has significant advantages in maintaining temperature stability while reducing energy consumption, and the PPO algorithm performs better than the DDPG algorithm. Compared with the PID algorithm, the PPO algorithm can save energy by 5.27%, and the temperature control effect can be improved by 3.27%,which indicates the feasibility of the ARL for implementation in real data centers.

Design and Optimization of Thermal Vacuum Sensor Test System Based on Thermoelectric Cooling

The performance of critical components in a sensor testing system may be compromised in a thermal vacuum environment as a result of the impact of extreme temperatures. Moreover, the precision of the angle measurement may be influenced by the thermal deformation effect. This paper presents a simulated analysis of the temperature regulation impact of the thermoelectric cooler (TEC) and outlines the design and optimization process of a sensor test chamber that can function within a consistent temperature range. The mathematical model of TEC is utilized to suggest a design choice, taking into account the aforementioned model, in a temperature-controlled environment with thermal vacuum circumstances. Moreover, the orthogonal test method is employed in combination with the FloEFD finite element analysis to validate the effectiveness of temperature control. In addition, the parameters of the radiation radiator are tuned and designed. Therefore, the temperature range difference inside the test system decreased by 20%. The thermoelectric temperature control system’s steady-state model is investigated using the PSpice simulation, based on the equivalent circuit theory. The discovered conclusions establish a theoretical foundation for improving the efficiency of temperature regulation. The design concepts presented in this work, particularly the optimization technique for radiation radiators in aerospace test equipment using thermoelectric cooling temperature control research and development, hold promise for practical implementation.

Temperature Control Effect on Cheese Whey Anaerobic Digestion with Low-Cost Tubular Digesters

Cheese whey (CW) is a worldwide abundant by-product of the cheese industry, which can be used for biogas production if further processing is not performed to produce other valuable food products. This study evaluates biogas production from CW in low-cost, tubular reactors, thus comparing the effect of temperature control. CW was monodigested in two tubular reactors at the pilot scale: one of them with temperature control (30 ± 3 °C) and the other one working at environmental conditions. The results show that CW could be monodigested in pilot scale tubular reactors, thus yielding high methane. Temperature control (30 ± 3 °C) at the pilot scale led to higher methane yields under all tested operating conditions, thus reaching 565.8 ± 20.9 L kg−1VS at an Organic Loading Rate (OLR) of 0.416 ± 0.160 kgVS L−1 d−1, which was higher than the maximum yield obtained without temperature control (445.6 ± 21.9 L kg−1VS) at 0.212 ± 0.020 kgVS L−1 d−1. Methane yield differences were attributed to the increase in temperature, thus leading to a more stable process and a higher degradation capacity. The increase in temperature is only worthwhile if adequate thermal insulation is used between the digester and the soil; otherwise, the increase in biogas production will not meet the digester’s heat demand. The anaerobic monodigestion of CW in low-cost tubular reactors is a promising alternative for CW valorization, thus leading to high biogas yields, which can be used in several energy applications replacing fossil fuels.

Effects of Optimal Temperature Control in Body Contouring Surgery: A Nonrandomized Controlled Clinical Trial.

Perioperative hypothermia in plastic surgery has underestimated risks, including increased risk of infection, cardiac events, blood loss, prolonged recovery time, and increased nausea, pain, and opioid usage. Inadequate preventive measures can result in up to 4 hours of normothermia restoration. The aim was to compare the impact of different strategies for normothermia during plastic surgery procedures and their relationship with clinical outcomes. A nonrandomized clinical trial was conducted in a single center in Bogota, Colombia. We enrolled adult patients undergoing body contouring surgery and divided them into 4 intervention groups with different measures to control body temperature. Univariate and bivariate analyses were performed, comparing several clinical symptoms to evaluate outcomes. A total of 197 patients were analyzed. Most of them were females (84.3%). Mean age was 38.6 years, and the median procedure duration was 260 minutes. Demographic and clinical characteristics did not exhibit significant differences between the groups. There were notable variations in temperature measurements at crucial moments during the surgical procedure among the groups, attributed to the implementation of distinct thermal protective strategies. Group comparisons showed a relationship between hypothermia and increased nausea, vomiting, shivering, pain, and additional analgesia requirements. Incorporation of active thermal protective measures, such as Blanketrol or HotDog, during body contouring procedures, markedly diminishes the risk of hypothermia and enhances overall clinical outcomes. Implementing these active measures to maintain the patient in a state of normothermia not only improves operating room efficiency but also leads to a reduction in recovery room duration.

Thermal Performance of Heat Sink Filled with Double-Porosity Porous Aluminum Skeleton/Paraffin Phase Change Material.

Phase change materials (PCMs) are used to cool high-power-density electronic devices because of their high latent heat and chemical stability. However, their low thermal conductivity limits the application of PCMs. To solve this problem, a double-porosity porous aluminum skeleton/paraffin phase change materials (DPAS/PCM) was prepared via additive manufacturing and the water-bath method. The thermal performance of the DPAS/PCM heat sink (HS) was experimentally investigated to examine the effects of the positive- and reverse-gradient porosity structures of the DPAS/PCM. The results show that a positive-gradient porosity arrangement is more conducive to achieving a low-temperature cooling target for LED operation. In particular, the temperature control time for the positive gradient porosity structure increased by 4.6-13.7% compared with the reverse gradient porosity structure. Additionally, the thermal performances of uniform porous aluminum skeleton/paraffin (UAS) and DPAS/PCMs were investigated. The temperature control effect of the DPAS/PCM was better than that of the UAS/PCM HS at high critical temperatures. Compared with the UAS/PCM HS, the temperature control time of the DPAS/PCM HS is increased by 7.8-12.5%. The results of this work show that the prepared DPAS/PCM is a high-potential hybrid system for thermal management of high-power electronic devices.

A novel battery thermal management based on composite phase change material with liquid-assisted cooling for different ambient temperatures

In this work, a thermal management system (TMS) employing the combination of composite phase change material (CPCM) and liquid cooling was developed for a lithium battery module. To enhance the temperature uniformity of the battery module, a new strategy was proposed creatively, which varied the thermal conductivity of the CPCM wrapping the battery depending on the position of the battery. Firstly, the thermal conductivity of CPCM was optimized for a single battery thermal management. Then, the temperature control effects of the proposed TMS were investigated numerically on the battery module. Results indicate the thermal conductivity of CPCM should not be more than 3 W/m·K. At 40 °C of ambient temperature, the only CPCM cooling can maintain the surface temperature of battery with 5C discharging within 44 °C, presenting excellent uniformity. At 45 °C, CPCM fails and liquid cooling can inhibit the temperature rise of the batteries, but increases the temperature inconsistency. Compared to the CPCM with constant thermal conductivity (3 W/m·K), the surface temperature difference of the battery module decreases from 5.30 to 2.95 °C employing CPCM with varying thermal conductivity (0.6–3 W/m·K). Decreasing coolant temperature can reduce the battery module temperature, but increase its temperature difference. The effectiveness of the varying λCPCM on the temperature uniformity of a battery module has also been verified by the designed experiment. This study can potentially provide significant guidance to the design of a lithium battery module based on the coupling CPCM and liquid cooling.

Simulation Study on Temperature Control Performance of Lithium-Ion Battery Fires by Fine Water Mist in Energy Storage Stations.

The combustion of lithium-ion batteries is characterized by fast ignition, prolonged duration, high combustion temperature, release of significant energy, and generation of a large number of toxic gases. Fine water mist has characteristics such as a high fire extinguishing efficiency and environmental friendliness. In order to thoroughly investigate the temperature control effect of fine water mist on lithium-ion battery fires. This study employs numerical simulation methods, utilizing PyroSim software to simulate the fire process in lithium-ion battery energy storage compartments. First, we focus on the variation patterns of flame, changes in combustion temperature, and heat release rate over time at environmental temperatures of 10, 25, and 35 °C. Subsequently, the suppression of flame, reduction in temperature, and changes in heat release rate are simulated for water mist in lithium-ion battery fires. The simulation results indicate that the environmental temperature has a considerable impact on the flame but a lesser effect on the heat release rate. Fine water mist effectively impedes the spread of thermal runaway between internal battery core cells, leading to a reduction in the flame size and a significant decrease in the maximum temperature and heat release rate. The numerical simulation results can provide scientific guidance for the prevention and control of fires in lithium-ion battery energy storage compartments.

Adaptive Network-Based Fuzzy Inference System–Proportional–Integral–Derivative Controller Based on FPGA and Its Application in Radiofrequency Ablation Temperature Control

The radiofrequency ablation temperature system is characterised by its time-varying, non-linear, and hysteretic nature. The application of PID controllers to the control of radiofrequency ablation temperature systems has a number of challenges, including overshoot, dependence on high-precision mathematical models, and difficulty in parameter tuning. Therefore, in order to improve the effectiveness of radiofrequency ablation temperature control, an adaptive network-based fuzzy inference system combined with an incremental PID controller was used to optimise the shortcomings of the PID controller in radiofrequency ablation temperature control. At the same time, the learning rate at the time of updating the consequence parameters was set by segmentation to solve the problem of poor control accuracy when the ANFIS-PID controller is implemented based on FPGA fixed-point decimals. Based on FPGA-in-the-loop simulation experiments and ex vivo experiments, the effectiveness of the ANFIS-PID controller in the temperature control of radiofrequency ablation was verified and compared with the PID controller under the same conditions. The experimental results show that the ANFIS-PID controller has a superior performance in terms of tracking capability and stability compared with the PID controller.

Hydrothermal analysis of parallel and symmetric microchannels with phase change slurry and porous fin designs

The dynamic information of microchannel systems with parallel and symmetric configurations is insufficient, which limits our ability to compare and optimize these systems in all directions. In this study, thermal and hydraulic characteristics in parallel and symmetric microchannel heat sinks (MCHSs) with porous fins cooled by phase change slurry are investigated. A 3-D steady state conjugate model is adopted to compare the effects of fin configuration, coolant type and structural parameters on hydrothermal properties of wavy MCHS. The variations of dimensionless parameters involving Nu, f, η (temperature control effectiveness) and PEF (performance evaluation factor) are considered to demonstrate the effectiveness of combined design on overall performance enhancement of wavy MCHS. Results indicate that lower temperature increment and higher pressure loss appear in wavy configuration with porous fins than in straight mode, and lowest thermal resistance arises in parallel porous fin design. At the narrow position of symmetric channel, the fluid changes from the low-speed drop-shaped micelle to high-speed bullet-shaped one with increasing A, which leads to higher Nu with larger pressure drop penalty. Due to the extended flow route and improved fluid mixing, η increases with decreasing wavelength in all cases, and η of porous microchannels with both phase change slurry and parallel fins is much larger than that of symmetric one and the one with only base fluid. Compared with wavy fin configurations with small and large ε, lower temperature and its more uniform distribution happen in the mode with medium porosity. In comparison with basic configuration, the parallel configuration with slurry as cooling medium has the maximum PEF value when the pore size is 0.14 mm, up to 1.64. Larger f increase occurs in wavy channel with increasing N, and the space shortening between adjacent channel cavities in symmetric mode makes the adjoining Dean vortices easier to contact and repel, thus making it appear larger rise of f than parallel mode. Compared with other channel parameters, it is not effective to improve the overall performance of wavy MCHS with porous fins by adjusting α. Overall, the throat effect of symmetric MCHS significantly occurs in channel configuration with larger A, bigger λ, lower ε, smaller dp, more N, and lesser α, leading to higher f rise than the parallel mode.

Preparation and characterization of phase change material emulsions and their applications in liquid cooling systems for wind turbines

In order to improve the effect of liquid cooling system for wind turbine, this study used ultrasonic preparation method, stearic acid as phase change material, sorbitan trioleate and sodium lauryl sulfate as compound surfactants successfully prepared stearic acid phase change material emulsion as a cooling medium for investigation. The characterization, thermophysical properties, and fluidity of stearic acid phase change material emulsions at varying concentrations were examined through differential scanning calorimetry, thermal constant analysis, and viscometry. To investigate the cooling effects, a stator axial liquid cooling model was developed for both water and a 14 % stearic acid phase change material emulsion. Findings revealed that the 14 % stearic acid phase change material emulsion exhibited a latent heat of phase change of 22.5 J/g, reaching a peak melting temperature of 68.7 °C. Additionally, the latent heat of solidification was measured at 21.08 J/g, accompanied by a peak solidification temperature of 60.3 °C. The maximum thermal conductivity reached 0.5801 W/(m·K), and the specific heat capacity peaked at 5219.8 J/(K·mol), marking a notable improvement of 1.26 times. Under an inlet temperature of 30 °C and a flow rate of 1 L/min, stearic acid phase change material emulsion effectively lowered the temperatures of the windings, stator, rotor, and casing by 19.2 °C, 23.6 °C, 19.2 °C, and 9.6 °C, respectively. stearic acid phase change material emulsion demonstrates excellent temperature control effectiveness at 3600 r/min and a low flow rate of 1 L/min, showcasing efficient energy utilization efficiency.

Chemical crosslinking porous polymers prepared by thiol-ene click reaction with two-sided MXene layers for highly efficient infrared stealth

As the capabilities of infrared detection advance, materials with a single working modes are no longer sufficient for the effect. Designing a multi-module cooperative infrared stealth composite material has become particularly important. However, materials with multiple working modules face challenges such as long procession and difficulty in integration. Therefore, we employed thiol-ene click reaction to prepare porous polymers as thermal insulation substrates, incorporated phase change microcapsules for heat absorption and temperature delay, and loaded two MXene layers at the top and bottom are low emissivity for infrared stealth and radiative heating, respectively. This sandwich-structured composite material exhibits a minimum infrared emissivity of 0.289 (3–5 μm) and 0.212 (8–14 μm), showing excellent camouflage capability for infrared thermal signals under an infrared camera, generating a temperature difference of about 61 °C with the hot target at 100 °C. Additionally, the bottom MXene layer used for radiative heating can raise the temperature of artificial skin by 2.5 °C. Furthermore, the as-prepared M28PP0.36M6 also demonstrates superior mechanical properties (300 kPa, 50 %). We believe that, due to the synergistic effects of temperature control and low emissivity, combined with advantages of facile preparation, it will become a promising candidate in the field of infrared stealth.

Increasing the Utilization of Solar Energy through the Performance Evaluation of Air-Based Photovoltaic Thermal Systems

Photovoltaic thermal (PVT) systems are attracting a significant amount of attention in research because they can generate electricity outside of daytime hours, unlike photovoltaic (PV) systems, and can increase efficiency and collect additional energy by reducing the temperature of PVT panels. However, a somewhat lower amount of collected energy is used in the summer than in the winter, and research on this issue is lacking. In this study, first, we experimentally evaluated the performance of PV and PVT systems by season and verified the improvement in the performance of the PVT system. Second, experiments were conducted to verify the enthalpy reduction via mist cooling and dehumidification, and the temperature and humidity control effect via mist cooling and dehumidification was verified. Based on our research findings, we propose a model that can be integrated with indoor ventilation systems to increase the solar energy utilization of PVT systems. Using the PVT system, we improved the panel power generation efficiency by up to 5.89% and generated up to a 38.0% higher collection efficiency than that of the PV system. The air that passed through the PVT system was then subjected to mist cooling and dehumidification to reduce its temperature and increase its humidity, resulting in a 23.2% reduction in enthalpy.

Temperature control for the synthesis of n-butylmagnesium bromide Grignard reagent based on n-octadecane/polystyrene microPCMs

Thermal runaway accounts for a high proportion of chemical safety accidents and poses a serious threat to the operational safety of personnel. Phase change materials (PCMs) have a high enthalpy of melting, if the latent heat energy of their phase change can be stored and used to absorb the heat released during thermal runaway, this phenomenon can provide a new approach for the control of reaction thermal runaway. In this work, microencapsulated phase change materials (microPCMs) were prepared by the suspension polymerization method using n-octadecane as the core material and polystyrene (PS) as the shell material. The prepared microPCMs had regular spherical morphologies with smooth surfaces, and the average particle size was 7.54 μm, the thermal conductivity was 0.05964 W/m∙K. The melting enthalpy of the microPCMs was 142.2 J/g, and the encapsulation percentage of the PCMs was 62.15%. The synthesis of the n-butylmagnesium bromide Grignard reagent occurred via a strong exothermic reaction, which was very likely to lead to overpressure venting once control was lost. The prepared microPCMs were applied as inhibitors in this reaction to investigate the temperature control effect under different operating conditions. The results showed that the amount of microPCMs added, and the timing of the addition affected the control effect. The addition of microPCMs could effectively reduce the reaction temperature and slow the rate of temperature increase. Even in the event of an emergency situation, such as a control failure, time could be gained for other emergency measures, effectively reducing the probability of thermal runaway accidents.

An intelligent heating system based on the Internet of Things and STM32 microcontroller

Under the rapid growth of Internet of Things technology, many households are moving towards smart solutions. Addressing the inflexibility of temperature control in traditional heating systems, this research focuses on designing an intelligent heating system. To enhance flexibility and intelligence, an intelligent heating system based on the Internet of Things and STM32 microcontroller is proposed. Furthermore, the study identifies limitations of traditional proportional-integral-derivative control methods and establishes an optimization control model for heating system output temperature based on the Dynamic Matrix Control algorithm. Results indicate that the system's web interface successfully draws temperature curves, displaying clear data on detected temperature and humidity. The output temperature optimization control model shows a temperature rise of 2 °C and a temperature control error index of 0.0543 during the initial heating stage, and a control error index of 0.0353 during the mid-heating stage when the valve relative opening is close to 0. And the temperature control effect is better than traditional PID control, fuzzy PID control, genetic algorithm based PID control, and predictive feedback predictive control, without obvious indoor temperature overshoot phenomenon, which has certain advantages. In conclusion, the proposed system and model exhibit favorable application outcomes, offering technological support for the intelligent management of heating systems.

Effect of Local Temperature Control on Fruit Maturation and Quality in Strawberry ‘Koiminori’

Effect of Local Temperature Control on Fruit Maturation and Quality in Strawberry ‘Koiminori’

High-precision and wide-range temperature measurement and control system of satellite-borne calibration blackbody

The accurate measurement and control of blackbody temperature can play an important role in radiometric calibration. A novel circuit suitable for the aerospace environment is designed to measure and control the temperature of the blackbody. A coarse-fine measurement method considering the wire resistance and self-heating effect of the platinum resistance is presented to calculate the resistance values of the platinum resistors. The precision of temperature measurement is improved using a line fitting algorithm with error calibration and temperature drift error compensation. A fuzzy self-adaptive PID controller is designed to improve the temperature control effect. The performances of the developed system are implemented on an FPGA/A3PE3000-FG484I controller board. The test results show that the device temperature measurement precision can reach ±0.03K for the entire temperature range 238 K to 367 K, the temperature stability is better than 0.02 K/20 s, and the temperature uniformity is better than 0.1 K.