Maximum Allowable Temperature Research Articles

An active thermal management strategy for switched reluctance drive system with minimizing current sampling delay

The reliability of switched reluctance drive system (SRD) can be improved by an effective thermal management strategy, when SRD is exposed to harsh environment and anything could happen throughout the life time. In order to avoid overtemperature fault of power converter, there are generally two methods: derating and switching frequency reduction. However, the derating methods will lead to insufficient power and even affect the safety of SRD. An active thermal management strategy for SRD with minimizing current sampling delay is proposed in this paper, which can ensure that the temperature of power converter will not exceed the maximum allowable temperature under any working condition by adjusting switching frequency. In the proposed strategy, the sampling method can ensure that the output performance of SRD at lower switching frequency is good as that of traditional sampling method at normal switching frequency by optimizing the sampling point.

Thermal performance analysis of a novel linear LED housing with inner and outer fins

There is an inverse relationship between the junction temperature of the light-emitting diode (LED) and its lifetime therefore, it is significant to operate it at low junction temperature. In this study, three different natural convection linear housing models were developed to cool mid-powered LED arrays, focusing on basic parameters such as fin structure, surface area, and wall thickness in the design of the models and thermal performance has been tested numerically and experimentally. The performance tests were carried out at five different ambient temperatures, 20, 25, 30, 35, and 40 °C. Compared to Model-1 (standard housing without fin) and Model-2 (thin housing with inner fin), the cooling effect of Model-3 (thin housing with inner+outer fin) is remarkably high, and this effect was more evident with the increase in ambient temperature. This impact has been achieved by increasing the surface area of Model-3 by almost 50%, although its mass has decreased more than twice. The maximum junction temperatures of Model-3 were approximately 2 °C lower than Model-1 and 5 °C lower than Model-2 in all experiments, with the presence of fins and the development of geometry. When the maximum allowable temperature rise is 94.68–101.25 °C and the 35 watts dissipated in the package, the average thermal resistances were found to be 1.12–1.38 °C/W. It is thought that these new-generation LED-based linear designs can be used to illuminate the work areas and they can replace compact lamp-based luminaires that work with direct and indirect lighting principles.

Interaction of temperature fields in an unlimited array of soil during the selection of low-grade heat by U-shaped probes of a geothermal heat pump units

The methodology and results of mathematical modeling of the unsteady process of selecting low-grade soil heat with a vertical U-shaped geothermal probe placed in a well of heat pump units (HPU), the free space of which is filled with a heat-conducting filler, are presented. The developed mathematical model is based on the joint use of two classical analytical methods: a source-drain adapted to the unsteady process of heat extraction from an unlimited soil mass, and a superposition method that allows one to quantify the effect of the interaction of the temperature fields of the downpipe and the riser pipe laid at a small distance from each other in one well. As a result, the main calculated dependencies underlying the developed mathematical model on which the computational experiment was performed were obtained analytically. The results of a computational experiment, performed on the example of a well with a vertical U-shaped soil probe, designed to select low-grade heat from an unlimited array of dry sand, are presented in graphs. An analysis of the results made it possible to identify the main factors affecting the intensity of heat extraction, justify the conditions for the effective operation of U-shaped probes in the wells of the soil contour of heat pump units, and quantitatively determine the maximum allowable temperature increment of the heated coolant according to the condition of efficient use of the heat transfer surface.

Friction stir incremental forming of polyoxymethylene: process outputs, force and temperature

ABSTRACT Despite good creep and fatigue durability, high resistance against chemicals and good surface finish, Polyoxymethylene (POM) has been sidelined in incremental sheet forming (ISF) literature due to its low formability at room temperature. This paper addresses the issue by deploying a cost-effective friction-induced heat at the tool-sheet interface. This work demonstrates a combined experimental, analytical, and numerical approach to investigate the effects of elevated temperature in ISF of POM. For this purpose, the formability of POM was first experimentally investigated under the interactive effects of the process parameters. Employing the membrane analysis approach, the stress state in the FSISF process was defined. The tool-sheet contact area was calculated as a function of toolpath and the relevant process parameters. The Johnson-Cook plasticity model was calibrated based on several universal mechanical tests at various temperatures and rates. Embedding the stress state, contact area, and the material model inside an algorithm developed by adopting the Finite Difference Method, force, friction-induced heat, and temperature at the tool-sheet interface were evaluated. Simulation results were validated by experimental outcomes. A threshold boundary for the maximum allowable tooltip temperature was established to avoid heat-induced defects while ensuring the sheet formability.

Integrated Design Method of Linear PM Machines Considering System Specifications

The system specifications should be considered in the practical design of linear machines, albeit mostly neglected in the previous studies. The main objective of this article is to propose a systematic design method of a coreless-type permanent magnet linear synchronous machine (PMLSM), satisfying all the constraints resulting from the system specifications. Based on the trapezoidal motion profile, an electromagnetic design model is developed by utilizing the 2-D field solutions and energy conversion principle. The thermal effects are incorporated into the design model by measuring the hot-spot temperature of the static winding coil, thereby setting the upper limits of current density. The differential evolution (DE) is then applied to the design model to search for optimal solutions without violating any of the constraints. As a result, the proposed model combined with DE provides the Pareto-optimal front belonging to the feasible regions where all system specifications (e.g., acceleration profile, maximum speed, maximum allowable temperature, load mass, and supply voltage) are satisfied. Finally, the validity of the design model is verified by both the finite element (FE) and experimental results.

Characterization of Florida, U.S. landfills with elevated temperatures

The occurrence of elevated temperatures within landfills is a challenging issue for landfill operators to detect and correct. Little is known regarding the causes of elevated temperatures (ETs) or the number of landfills currently operating under such conditions. Therefore, the goal of this research was to determine which landfills within Florida have been impacted by ETs, and to develop a more complete understanding of the factors that may lead to these landfills becoming elevated temperature landfills (ETLFs). Historical landfill gas wellhead data, waste deposition reports, and landfill site geometry were collected for 27 landfill cells through the Florida Department of Environmental Protection electronic document management system, OCULUS database and from landfill operators and owners. These data were evaluated to quantify the characteristics that result in landfills having ‘elevated’ temperatures. Gas data included landfill gas temperatures and methane, carbon dioxide, and balance gas content. Furthermore, landfill maps were created in ArcGIS to observe spatial distribution of ETs in landfills over time. Upon analysis of the landfill gas wellhead data, it was discovered that 74% of studied landfill cells had ET readings; regulatory limits specify a maximum allowable gas temperature of 55 °C (131 °F). It was discovered that 37% of landfill cells contained MSW ash; of these cells, 90% of them are considered ETLFs. ETLF cells are on-average double the site area and approximately 6 m deeper than the average non-ETLF cell. Furthermore, results suggest that heat propagation in most landfills is limited; however, heat propagation is possible if gas wells are turned off for an extended time period.

Optimization and Design of Regenerative Cooling Channel for Scramjet Engine

In this paper, the optimization model and numerical calculation verification model of the regenerative cooling channel structure of the scramjet engine are established, and the structural parameters of the regenerative cooling channel of the scramjet engine are optimized and numerically verified. The results show that the established optimization model of the regenerative cooling channel structure of the scramjet engine can meet the design requirements; after the structure optimization, the wall temperature change trend is basically the same as the original design change trend, and the overall temperature is low; the central flow calculated by the optimized configuration calculation, but the pressure loss of kerosene in the cooling channel is small. The oil temperature and convection heat transfer coefficient are large; the inner wall and fins of the optimized configuration are thinner, the channel height is higher, and the width is narrower, which can effectively increase the convection heat transfer efficiency of the cooling channel, which can ensure that the material temperature is not Exceeding its maximum allowable temperature can make the pressure loss relatively low.

Embedded Ocv Based Model for State of Health Monitoring in a BMS

Lithium ion batteries degrades with time. Battery diagnostics links observable changes in cell parameters to changes that have occurred inside the cell. More accurate diagnosis means a better insight into these internal changes which can aid in predicting failure modes, remaining life, aide in optimising future use.In the case of electric vehicles, an on-board battery management system (BMS) could implement these diagnostic techniques to give real time information on the internal state of the pack. It can then dynamically adjust parameters such as state of charge (SOC) window, maximum power and maximum allowable temperature to optimise performance and pack longevity.Models capable of predicting Li-ion battery health with higher accuracy are highly advanced, and computationally exhaustive requiring complex physics-based models or equivalent circuit models (ECM) that require exhaustive parameter fitting. Other techniques require measurements or hardware which are not available in typical applications and so are only suited to lab-based diagnostics.Current diagnostic techniques are not suitable for in-situ applications; either the BMS does not have the computational capacity to run the models, or the measurements required are not available outside a laboratory environment. In this work, we propose an Open Circuit Voltage (OCV) based model that predicts the degradation of a cell accurately without needing extensive computational capacity.This model has been embedded in a microcontroller with limited computing power which could form part of the BMS system that better predicts the state of health of the cell. The model uses the open circuit potentials of each electrode and fits them to the full cell voltage in order to identify the degradation modes. Typical modes include Loss of Lithium (LLI) and Loss of Active Material from either electrode (LAM).The model does not require the solving of concurrent complex equations or the fitting of extensive parameters to an equivalent circuit whilst still being able to provide accurate insight into the cell’s internal changes.Results from this work demonstrate the usefulness of such a system in electric vehicle and paves the way for implementation of smarter BMS in electric vehicles by manufacturers. This unlocks the potential to predict and increase the longevity of a battery pack whilst still providing optimal performance to the vehicle.

Determination of the kinetics of the process of pumpkin seeds vibrational convective drying

Experimental studies of the drying process of high-moisture pumpkin seeds in a vibrating dryer are carried out. The research is caused by the need to solve the problem of fast and high-quality post-harvest treatment with minimal cost. Existing technologies and equipment do not ensure high performance of the drying process in the post-harvest period or carry it out with significant expenses of time and resources. The main objective of the study is to determine the rational parameters of the process and equipment for drying pumpkin seeds. As a result of the experimental studies of the kinetics of pumpkin seeds vibrational convective drying, rational process parameters were obtained, i. e. the maximum allowable temperature of the drying agent is t da =50 °С, which corresponds to the maximum allowable heating temperature of seeds t h2 =46.7 °С. At this temperature, the grain retains conditional values of germination ability and energy. The maximum allowable temperature is 0.3 °C lower than the maximum allowable heating temperature for pumpkin seeds. The results of the study of the intensification of vibration exposure indicate a direct relationship between the vibration frequency of the drying chamber and drying duration: the higher the frequency, the greater the intensity of vibration-convection drying, as well as a reduction in drying duration with increasing vibration amplitude. The obtained results confirm the feasibility of using a filtration-convective vibrating dryer, which ensures compliance with rational drying parameters, i. e. temperature and speed of the drying agent, amplitude, frequency, and filling of the working chamber. The combination of these parameters allows drying the seed material with minimal cost and maintaining its high quality

Performance evaluation of concentrator photovoltaic systems integrated with a new jet impingement-microchannel heat sink and heat spreader

Thermal regulation of concentrator photovoltaic (CPV) systems is of great importance to keep silicon layer temperature within the maximum allowable temperature range, as it enhances overall performance and avoids potential solar cells damage. Therefore, a novel jet impingement mini- and- micro channel heat sink with a heat spreader integrated with a CPV system is designed. To evaluate the performance of the developed system, a three-dimensional conjugate thermo-fluid model for the solar cell layers, jet impingement with microchannel flow, and heat spreader is established. This model is numerically solved, and results are validated using the available measurements. The new system is then compared using several heat sink designs including a jet impingement-mini-channel with and without a heat spreader at different concentration ratios (CR) and coolant Reynolds numbers (Re). The findings indicate that at CR = 20, integrating a jet impingement-micro-channel heat sink, and a heat spreader with the CPV system accomplishes a uniform silicon layer temperature distribution with the lowest average temperature compared to other designs. In addition, the established design attains the highest net electrical power and electrical efficiency. The results of the current study demonstrate the effectiveness of combining active and passive cooling methods for thermal management of the CPV systems.

Cryogenic Air Supply for Cooling Built-in-Place Refuge Alternatives in Hot Mine

Built-in-place (BIP) refuge alternatives (RAs) are designed to provide a secure space for miners who cannot escape during a mine emergency. Heat and humidity buildup within RAs may expose miners to physiological hazards such as heat stress. To minimize the risk of heat stress, Title 30 Code of Federal Regulations (CFR), or 30 CFR, mandates a maximum allowable apparent temperature (AT) for an occupied RA of 35 °C (95 °F) (MSHA 2008 [1]). The National Institute for Occupational Safety and Health (NIOSH) has conducted extensive research on the thermal environment of occupied RAs intended for use in underground coal mines. NIOSH research has demonstrated that a fully occupied BIP RA can exceed the AT limit by > 5.6 °C (10 °F) in mines with elevated mine strata and air temperatures (Bissert et al. 2017 [2]). In this circumstance, an RA cooling system could provide a solution. This paper provides an overview of test methodology and findings as well as guidance on improving the performance of a cryogenic air system prototype by optimizing the flow rate, increasing the tank storage capacity, and improving the efficiency of the heat exchanger of the cryogenic system. This may enable BIP RAs to meet the 35 °C (95 °F) AT limit in mines with elevated temperatures. The information in this paper is useful for RA manufacturers and mines that may choose to implement a cryogenic air system as a heat mitigation strategy.

Temperature-Based Criteria for Opening Newly Laid Repaired Asphalt Pavement Sections to Traffic

To avoid premature damage, a newly laid asphalt pavement repair must be allowed to cool sufficiently before opening to air traffic. This study examines the variations of temperature within different repaired asphalt layers during cooling, and makes recommendations with regard to the choice of temperature-based criteria for determining the earliest time to open a newly laid asphalt pavement section to air traffic in a busy airport. Using finite element simulation analysis, the cooling patterns of asphalt layers under the following conditions were studied: three different weather conditions (sunny daytime, cloudy daytime, and nighttime) with three different wind speeds. It is shown that the common practice of relying on surface temperature to determine the time for opening to traffic is unsatisfactory. This is because under most paving conditions, a large proportion of the newly laid asphalt layer would still have temperatures higher than the surface temperature. From finite element analysis for different paving and environmental conditions, it is recommended that the temperatures at an interior point be measured at either 1/2, 2/3, or 3/4 depth, and that nighttime paving be preferred. This study shows that for common asphalt pavement repairs of thicknesses up to 150 mm, taking the temperature at either 2/3 or 3/4 depth as the guide, a repaired asphalt layer, when opened to air traffic, would have its internal maximum temperature kept within 2°C of the preset maximum allowable temperature. If the 1/2 depth temperature is selected as a guide, a margin of within 4°C of the preset maximum allowable temperature can be achieved.

Can the selectivity of phosphonium based ionic liquids be exploited as stationary phase for routine gas chromatography? A case study: The use of trihexyl(tetradecyl) phosphonium chloride in the flavor, fragrance and natural product fields

Room temperature ionic liquids (ILs) are well established stationary phases (SPs) for gas chromatography (GC) in several fields of applications because of their unique and tunable selectivity, low vapor pressure and volatility, high thermal stability (over 300 °C), and good chromatographic properties. This study is focused on an IL based on a phosphonium derivative (trihexyl(tetradecyl)phosphonium chloride, [P66614+] [Cl−]), previously shown to be suitable as a gas chromatographic SP because of its unique selectivity. In particular, it aims to establish the operative conditions to apply [P66614+][Cl−] to routine analysis of samples containing medium to high volatility analytes with different polarity, organic functional groups and chemical structure. In the first part, the study critically evaluates long term [P66614+][Cl−] column stability and maximum allowable operating temperatures (MAOT). The relatively low MAOT (210 °C) requires the adoption of a dedicated approach for analytes eluting above this temperature based on a suitable combination of efficiency and selectivity, and column characteristics (length, inner diameter and film thickness) and operative conditions. The performance of [P66614+][Cl−] as a GC SP have been validated through the Grob test, a model mixture of 41 compounds of different polarity, structure, and with different organic functional groups in the flavor and fragrance field, a standard mixture of 37 fatty acid methyl esters, some essential oils containing pairs or groups of compounds of different volatility critical to separate in particular peppermint, thyme, oregano, sandalwood and frankincense. The above approach has produced highly satisfactory separations with all of the samples investigated.

Exergy Analysis of Heat Recovery Steam Generator: Effects of Supplementary Firing and Desuperheater

Abstract Comprehensive exergy analysis of a heat recovery steam generator (HRSG) with two levels of delivered pressure is presented. The effects of supplementary firing as well as desuperheater set-point are considered to evaluate the exergy destruction of HRSG components. Burner firing rate is limited to a value that corresponds to the maximum allowable temperature of tube metal of high-pressure (HP) superheater. According to the exergy analysis performed in the current study, the exergy efficiency of HRSG is about 80% which means 20% of flue gas exergy (entering HRSG) is dissipated by HRSG destruction (∼14%) and stack exergy loss (∼6%). The stack exergy loss drops continuously as supplementary firing raises. It has also been determined that increasing the rate of supplementary firing boosts the exergy efficiency in the absence of water spray and reduces it when desuperheater is working. In addition, the exergy delivered to steam turbine shows a linear growth with burner heat while it is hardly affected by the set-point of desuperheater. Also, it is found that exergy loss through the stack is not sensitive to desuperheater set-point while it is on the decrease as burner duty raises. HP steam flow will raise with increasing the firing and/or decreasing the desuperheater set-point. HP evaporator has the most contribution in exergy destruction among HRSG components (∼40%), whereas HP superheater and desuperheater are components with a maximum sensitivity of exergy destruction to the amount of water spray.

Analytical Prediction of Optimal Split Ratio for Short-Time Duty PM Brushless DC Motors Considering Winding Thermal Limitation

ABSTRACT The temperature gradient of high-torque-density short-time duty permanent magnet (PM) brushless DC motors (BLDCM) is large. Increasing the torque will cause the copper loss and the winding temperature to rise rapidly, which will lead to the risk of the winding insulation damage. A split ratio optimization method is proposed to raise the torque considering winding temperature limitation in this paper. The analytical relationship between the torque, the losses and the split ratio is derived. The transient temperature of the winding is calculated analytically based on the expressions of this analytical relationship. The maximum allowable temperature rise of the winding is converted to the optimization constraint. The optimal split ratio is calculated and the maximum torque within the temperature limit range is obtained. The method is verified by finite element (FE) simulation and experimental test. The FE predicted optimal split ratio value is equal to the analytically predicted value. The error between the simulated and calculated torque is less than 5.7%. The maximum error between measured and analytically predicted temperature is 7.2%. The verification results show that the proposed method can accurately calculate the optimal split ratio and maximizes the torque within the winding temperature limitation.

Optimum Network Ageing and Battery Sizing for Improved Wind Penetration and Reliability

A multiobjective framework that optimises the uprating of the line’s real-time thermal rating and capacity of battery storage against wind curtailment, network ageing and reliability is proposed. The two enhancements are limited to the accumulated expected amount and duration of wind power losses of each wind farm bus. In the framework, actual conductor properties, line failures due to thermal effects, weather data, battery operation policy and wind farm model are considered. The trade-off of the optimisation criteria, the Pareto front, is solved using the non-sorting genetic algorithm and fuzzy decision-making method. Results show that the conductor maximum allowable temperature affects all the three optimisation parameters, but battery efficiency only affects wind curtailment level.

Comparison of Heat-Pipe Cooling System Design Processes in Railway Propulsion Inverter Considering Power Module Reliability

In this paper, the effect of the heat-pipe cooling system design processes on the reliability of the power module in a railway propulsion inverter was investigated. The existing design processes for the heat-pipe cooling system guarantee that the junction temperature of power devices does not exceed the maximum allowable junction temperature when the railway propulsion inverter operates under its mission profile; therefore, each step of the design process was reviewed to analyze the effect of the heat-pipe cooling system. Based on the processes, in the calculation for the required thermal resistance of the heat-pipe cooling system, two difference losses were considered with the thermal resistances of the insulated gate bipolar mode transistor (IGBT) module and the thermal grease at an interface between the baseplate of IGBT module and heat-pipe cooling system. The control scheme and mission profile of the train were taken into account to calculate the power losses. Then, the designed heat-pipe cooling systems were compared in terms of the size and weight. In addition, the junction temperatures and lifetimes of the power module with heat-pipe cooling systems designed by different power losses were estimated and compared. Finally, guidelines for a heat-pipe system cooling design are proposed.

A Gas Turbine Cooled-Stage Expansion Model for the Simulation of Blade Cooling Effects on Cycle Performance

Modern gas turbine firing temperatures (1500–2000 K) are well beyond the maximum allowable blade material temperatures. Continuous safe operation is made possible by cooling the HP turbine first stages, nozzle vanes and rotor blades, with a portion of the compressor discharge air, a practice that induces a penalty on the thermal efficiency cycle. Therefore, a current issue is to investigate the real advantage, technical and economical, of raising maximum temperatures much further beyond current values. In this paper, process simulations of a gas turbine are performed to assess HP turbine first-stage cooling effects on cycle performance. A new simplified and properly streamlined model is proposed for the non-adiabatic expansion of the hot gas mixed with the cooling air within the blade passage, which allows for a comparison of several cycle configurations at different turbine inlet temperatures (TIT) and total turbine expansion ratio (PR) with a realistically acceptable degree of approximation. The calculations suggest that, at a given PR, the TIT can be increased in order to reach a higher cycle efficiency up to a limit imposed by the required amount and temperature of the cooling air. Beyond this limit, no significant gains in thermal efficiency are obtained by adopting higher PR and/or increasing the TIT, so that it is convenient in terms of cycle performance to design at a lower rather than higher PR. The small penalty on cycle efficiency is compensated by the lower plant cost. The results of our model agree with those of some previous and much more complex and computationally expensive studies, so that the novelty of this paper lies in the original method adopted on which the proposed model is based, and in the fast, accurate, and low resource intensity of the corresponding numerical procedure, all advantages that can be crucial for industry needs. The presented analysis is purely thermodynamic and it includes no investigation on the effects of the different configurations on plant costs. Therefore, performing a thermo-economic analysis of the air-cooled gas turbine power plant is the next logical step.

Influence of Solar Radiation Heat Input into Room on Level of Economically-efficient Thermal Protection of Building

Techniques for choosing an energy and economically feasible thermal protection of buildings in the climatic conditions of Moscow are discussed earlier. An important basis of these techniques is that it was possible to identify the thermal parameters on the basis of which the generalization of the basic energy and economic indicators of the building, depending on its thermal protection, was carried out. The methods were tested for buildings whose working day lasts from 9 am to 6 pm with various internal heat generation. In this case, it was believed that solar radiation is completely obscured. From consideration of the effect of heat gains on energy-efficient thermal protection, it was found that with increasing heat gains, the load on heating systems decreases regardless of the level of heat protection, and the load on the room cooling systems increases more with higher thermal protection than with low thermal protection. However, there are buildings of a number of functional purposes in which solar radiation is partially obscured or not obscured at all. These include some commercial, residential and other buildings. Accounting for heat gains from solar radiation, with variable intensity throughout the year, makes significant adjustments to the choice of the level of thermal protection. This is due to the fact that often cooling of the room is required during periods when the outside air temperature is below the maximum allowable temperature of the room. During these periods, enhanced thermal protection is an obstacle to the natural outflow of heat from the premises. Calculations showed that the higher the heat gain from solar radiation, the smaller the proportion of buildings it is energetically feasible to warm according to the basic standards stipulated in SP 50.13330.2012. And although it is not energetically feasible to carry out thermal insulation for sanitary and hygienic requirements, the conclusions about the benefits of building insulation with reduced heat transfer to the walls and coatings of a building are economically significant. It is also important that when identifying an economically feasible thermal protection of a building, it is necessary to take into account all the components of financial expenses that are affected by the thermal protection of a building. The calculations also showed that an increase in the cost of heat and electricity over time changes the thermal performance of buildings for which this or that thermal protection is economically feasible.

Analysis on the reliability of R290 rotary compressor in the high ambient temperature

The R290 rotary compressor is suggested to use in split room air conditioners in hot climate areas for its higher efficiency, environmental-friendly, and lower discharge temperature. However the higher condensing temperature and pressure would result in reliability problems. In this paper the reliability of rotary compressor with R290&MO and R290&SO (mainly including the motor reliability; the oil sump viscosity, temperature and solubility; the oil film thickness of bearings) under the ambient temperature of 35 °C,46 °C,55 °C were studied experimentally and numerically. The results show that the motor temperature in R290 rotary compressor is lower than the allowable maximum temperature even under the condition of EXT/8 (condensing temperature = 70 °C). In addition, the oil sump viscosity of either synthetic oil (SO) or mineral oil (MO) decrease with the increase of ambient temperature (SO: from 4.7cp to 3.1cp; MO: from 2.2cp to 1.6cp), while under any condition, the solubility of SO (15%–16%) or MO (22%–25%) varies little. Besides, in the high ambient temperature (46 °Cand 55 °C), it is feasible to increase suction superheat to satisfy the proper viscosity when MO is used, while it is infeasible to SO. Influenced by oil viscosity and load, the oil film thickness of main bearing, sub bearing and eccentric bearing decrease with the increase of ambient temperature.