Modelling, Simulation, and Experimental Validation of a Thermal Cabin Model of an Electric Minibus

Climate control is an advanced air conditioning system that allows controlling the temperature in the machinery cabin more effectively in any weather conditions. Today, almost all new road-building machinery is equipped with this system. This system allows adapting the temperature in the cabin according to your needs more effectively. Climate control allows controlling the climate in the cabin regardless of the weather conditions outside the machine. Climate control works just like home air conditioners, thanks to the automatic control of the heating, ventilation and air conditioning systems. With the help of electronics, the temperature is automatically maintained at the level set by the driver. This system is necessary not only to maintain a stable temperature in the cab, but also to maintain the efficiency and concentration of the driver. However, there is no air conditioning system in the old road construction machines. In the Republic of Sakha (Yakutia) the material and technological foundations in many road enterprises are outdated for now. And in order to keep the driver operating and protect his health, this article discusses the possibility to equip road-building machinery with climate control. THE Volvo BL61B forklift was chosen as an example. This machine initially lacked a climate control system, but thanks to a temperature control device, it was possible to achieve the optimum temperature in the cabin.

<div class="section abstract"><div class="htmlview paragraph">Diesel engines are the versatile power source and is widely used in passenger car and commercial vehicle applications. Environmental temperature conditions, fuel quality, fuel injection strategies and lubricant have influence on cold start performance of the diesel engines. Strategies to overcome the cold start problem at very low ambient temperature include preheating of intake air, coolant, cylinder block. The present research work investigates the effect of coolant temperatures on passenger car diesel engine’s performance and exhaust emission characteristics during the cold start at cold ambient temperature conditions. The engine is soaked in the -7°C environment for 6 hours. The engine coolant is preheated to the desired coolant temperatures of 10 and 20°C by an external heater and the start ability tests were performed. The coolant temperature of 10°C in the -7 °C environment improved the fuel combustion and thereby reduced the cranking period by half; reduced the peak HC emissions and NOx emissions by 85% and 30% respectively. The cold ambient conditions increased the accumulation mode particles by 60% and decreased the nucleation particles by 70% compared to that of normal ambient temperature (+20°C). The coolant temperature of 10°C decreased the accumulation particles by ∼ 30% compared to normal ambient temperature. The number count of larger particulates of size 100-1000 nm doubled whereas particulates of diameter less than 100 nm reduced by 20% at -7°C environment compared to +20°C. Coolant temperature of 20°C in the low ambient temperature conditions decreased the total particulate mass to 1/7<sup>th</sup> of that at cold ambient conditions. The coolant heating strategy improved the cold start performance of the engine at cold ambient temperature conditions and thereby would reduce the overall driving cycle emissions as well.</div></div>

최근 기후변화와 기상이변 등으로 동절기에 더욱 가혹한 기상 조건이 자주 보고되고 있다. 그러나, 철도차량의 난방용량은 이렇게 극도로 추운 기후환경에서는 객실을 난방하기에 충분하지 않은 경우가 많으며, 이는 난방에 대한 승객의 민원을 야기하는 주요 원인이 되고 있다. 본 연구에서는 외기 온도와 난방 출력이 객실 온도에 미치는 영향을 알아봄으로써 차량의 난방용량에 따른 운행 가능한 외기온도를 실험적으로 도출하고자 하였다. 실험방법으로는 우선 시험용 철도차량을 대형 기후환경 챔버에 넣고, 다양한 외기온도조건을 모사하였다. 난방 장치 출력의 영향은 난방 장치의 출력을 변화시키면서 객실의 온도를 측정하여 조사하였다. 외기온도가 <TEX>$-10^{\circ}C$</TEX>인 조건에서는 난방기의 출력을 최대로 한 경우에도 객실의 평균 온도는 <TEX>$14.0^{\circ}C$</TEX>에 불과하여, 동절기의 객실온도 최소 요구조건인 <TEX>$18^{\circ}C$</TEX>보다 훨씬 낮았으나, 외기 온도가 <TEX>$0^{\circ}C$</TEX>와 <TEX>$10^{\circ}C$</TEX>인 경우의 객실온도는 각각 <TEX>$26.1^{\circ}C$</TEX>와 <TEX>$34.0^{\circ}C$</TEX>였다. 내삽법으로 계산한 결과 객실 내부 온도를 <TEX>$18^{\circ}C$</TEX> 이상으로 유지할 수 있는 최저 외기온도는 <TEX>$-6.7^{\circ}C$</TEX>임을 알 수 있었다. 객실 내부에서의 수직 온도 차이는 난방기 출력이 높을수록, 외기온도가 높을수록 커서 10 K 이상 차이가 나는 경우도 있었다. 그러나, 수평 온도 차이는 난방기 출력이나 외기온도에 무관하게 최대 2 K 이하로 매우 낮게 나타났다. 따라서, 우수한 난방성능을 확보하기 위해서는 수직 온도 차이를 줄이는 것이 중요함을 알 수 있었다. Recently, abnormally cold weather has been reported more frequently in winter due to the climate change and abnormal weather changes. On the other hand, the heating capacity of a railcar may be not enough to warm the cabin under severe cold climatic conditions, which is one of the reasons for the passengers' complaints about heating. In this study, the effects of ambient temperature and heater power on the cabin temperature was investigated to obtain the minimum ambient temperature for the tested railcar. The test railcar was placed in a large-climatic chamber, and various ambient temperature conditions were simulated. The effects of the heater output were investigated by monitoring the cabin temperature under a range of heater output conditions. The mean cabin temperature was <TEX>$14.0^{\circ}C$</TEX>, which was far lower than the required minimum temperature of <TEX>$18^{\circ}C$</TEX>, under a <TEX>$-10^{\circ}C$</TEX> ambient temperature condition with the maximum heat power. When the ambient temperature was set to <TEX>$0^{\circ}C$</TEX> and <TEX>$10^{\circ}C$</TEX>, the maximum achievable cabin temperature was <TEX>$26.1^{\circ}C$</TEX> and <TEX>$34.0^{\circ}C$</TEX>. Through calculations using the interpolation method, the minimum ambient temperature to maintain an <TEX>$18^{\circ}C$</TEX> cabin temperature was <TEX>$-6.7^{\circ}C$</TEX> for this car. The vertical temperature difference was higher with a higher power output and higher ambient temperature. The maximum vertical temperature difference was higher than <TEX>$10^{\circ}C$</TEX> in some cases. However, the horizontal temperature difference vs. low temperature (< <TEX>$2^{\circ}C$</TEX>) was independent of the power output and ambient temperature. As a result, it is very important to reduce the vertical temperature difference to achieve good heating performance.

The heating, ventilation and air conditioning (HVAC) system negatively affects the electric vehicle (EV) driving range, especially under cold ambient conditions. Modern HVAC systems based on the vapour-compression cycle can be rearranged to operate in the heat pump mode to improve the overall system efficiency compared to conventional electrical/resistive heaters. Since such an HVAC system is typically equipped with multiple actuators (compressor, pumps, fans, valves), with the majority of them being controlled in open loop, an optimisation-based control input allocation is necessary to achieve the highest efficiency. This paper presents a genetic algorithm optimisation-based HVAC control input allocation method, which utilises a multi-physical HVAC system model implemented in Dymola/Modelica. The considered control inputs include the cabin inlet air temperature reference, blower and radiator fan air mass flows and secondary coolant loop pumps’ speeds. The optimal allocation is subject to specified, target cabin air temperatures and heating power. Additional constraints include actuator hardware limits and safety functions, such as maintaining the superheat temperature at its reference level. The optimisation objective is to maximise the system efficiency defined by the coefficient of performance (COP). The optimised allocation maps are fitted by proper mathematical functions to facilitate the control strategy implementation and calibration. The overall control strategy consists of superimposed cabin air temperature controller that commands heating power, control input allocation functions, and low-level controllers that ensure cabin inlet air and superheat temperature regulation. The control system performance is verified through Dymola simulations for the heat pump mode in a heat-up scenario. Control input allocation map optimisation results are presented for air-conditioning (A/C) mode, as well.

One of barriers for the present heat pump system’s application in an electric vehicle was decreased performance under cold ambient conditions due to the lack of evaporating heat source. In order to improve the heat pump’s performance, a high-pressure side chiller was additionally installed, and the tested heat pump system was modified with respect to refrigerant flow direction along with operating modes. In the present work, the performance characteristics of the heat pump system with a high-pressure side chiller for light-duty commercial electric vehicles were studied experimentally under hot and cold ambient conditions, reflecting real road driving. The high-pressure side chiller was located after the electric compressor so that the highest refrigerant temperature transferred the heat to the coolant. The controlled coolant with discharged refrigerant from the electric compressor was used to heat up the cabin, transferring heat to the inlet air like the internal combustion engine vehicle’s heating system, except with unused engine waste heat. In the cooling mode, for the exterior air temperature of 35 °C and interior air temperature of 25 °C, cooling performance along with the compressor speed showed that the system efficiency decreased by 16.4% on average, the cooling capacity increased by 8.0% on average and the compressor work increased by 27% on average. In heating mode, at the exterior and interior air temperature of −6.7 °C, compressor speed and coolant temperature variation with steady conditions were tested with respect to heating performance. In transient mode, to increase coolant temperature with a closed loop from −6.7 °C, tested system characteristics were studied along the compressor speed with respect to heating up the cabin. As the inlet air of the HVAC was maintained at −6.7 °C, even though the heat-up rate of the cabin room was a little slow, the cabin temperature reached 20 °C within 50 min and the temperature difference with the ambient air attained 28.7 °C.

We measured pulmonary function in 12 healthy volunteers before and at 5-min intervals for 30 min following treadmill exercise of 30 min duration performed under control (20 degrees C) and cold (-11 degrees C) ambient temperatures. Post-run changes in forced vital capacity (FVC), residual volume (RV) and peak expiratory flow rate were similar between the two temperature conditions. FVC decreased slightly but significantly 5 min post-run (-0.25 +/- 0.20 l and -0.21 +/- 0.20 l, for control and cold conditions respectively) and returned to baseline by 30 min. RV increased significantly post-exercise (+0.07 +/- 0.09 l and +0.14 +/- 0.1 l, control and cold respectively) and remained elevated for 30 min. Forced expired volume in 1 s was not significantly different following either run. Post-exercise, maximum mid-expiratory flow rate and flows at 50% and 25% of vital capacity were not significantly different between warm and cold conditions. These data suggest that changes in lung volumes following exercise under cold ambient conditions are similar to changes seen following warm exercise of similar duration. In non-asthmatics, moderate exertion under cold ambient conditions does not appear to cause clinically significant decreases in expiratory flow rates as compared to similar exertion under warm conditions.

Mobile machine electrification faces challenges as efficiency, cost, reliability, and performance lead to an increased focus on an integrated thermal management system (ITMS) and heat load reductions. Benefits such as waste heat recycling is considered a key feature of ITMSs but requires better understanding of thermal load distributions. This paper provides a thermal load analysis of a battery powered excavator-loader—often referred to as backhoe loader—during excavating and transportation in cold and hot ambient conditions. The analysis is based on measurements and data from an existing series-hybrid electric version. The results show that the working hydraulic system is the highest potential thermal load contributor corresponding to 71–75% of the total thermal load during excavating. The potential cooling demand reduction in cold ambient conditions by recycling waste heat during transportation is 38% compared to 10% during excavating.

Enhanced absorption house connection station for low district heating return line temperatures

Influence of superheat and expansion ratio on performance of organic Rankine cycle-based combined heat and power (CHP) system

To determine the effect of cold ambient conditions on proprioception and cognitive function in elite alpine skiers. 22 high-level alpine skiers and 14 control participants performed a proprioceptive-acuity (active movement-extent discrimination) and a cognitive (planning task) test in cold (8°C) and temperate (24°C) ambient conditions. All participants displayed an increase in thermal discomfort and the amount of negative affects in the cold environment (all P < .05). Average proprioceptive acuity was significantly better in the elite skiers (0.46° ± 0.12°) than in the control group (0.55° ± 0.12°) (P < .05) and was not affected by cold ambient conditions, except for a shift in the pattern of error (over- vs underestimation, P < .05). Cognitive performance was similar between elite skiers and control participants in temperate environments but decreased in the cold in the control group only (P < .05) becoming lower than in elite skiers (P < .05). Elite alpine skiers showed a significantly better proprioceptive acuity than a control population and were able to maintain their performance during a cognitive task in a cold environment.

In most tokamaks, additional heating or extra power input is used to achieve the necessary plasma parameters such as temperature, confinement time, etc. This makes it possible to address current scientific challenges and conduct advanced research. The KTM tokamak will implement additional power input into the plasma using ion-cyclotron heating, as specified in the design. The additional plasma heating system on the KTM consists of four identical high-frequency generators, each with a capacity of 2 MW. No other systems for additional power input and plasma heating are provided on the KTM tokamak. Before operating such systems in normal mode, debugging and testing are conducted using load equivalents. This article presents the calculation of an active load equivalent. Based on the calculation results, the shape and geometric dimensions that ensure the absorption of up to 300 kW of high-frequency power are determined. The dimensions and main parameters of the load equivalent design for the additional high-frequency plasma heating system of the KTM tokamak have been determined. The calculations were carried out based on the assumption that the most preferable option is to create the load equivalent in the form of a resonator with an absorber made of saline aqueous solution. Experimental results from debugging using the developed active load equivalent are also presented. It has been demonstrated that with the developed load equivalent, it is possible to successfully carry out the necessary tests and adjustments of a high-power generator, and to prepare the additional power input system on the KTM tokamak for further debugging and switching to operation under plasma load.

&lt;div class="section abstract"&gt;&lt;div class="htmlview paragraph"&gt;Thanks to greatly increased energy density of battery, the average driving range of an electric vehicle has been advanced quite a lot. However, drastic reduction of driving range in cold ambient conditions still greatly restricts the wide application of electric vehicles.&lt;/div&gt;&lt;div class="htmlview paragraph"&gt;This paper presents a methodology of establishing multi-discipline coupled full vehicle model in AMESim to investigate the energy consumption of a pure electric vehicle in cold ambient conditions. Different strategies of battery heating through Positive Temperature Coefficient (PTC) part and/or combination of Motor Waste Heat Recovery (MWHR) were also investigated to study whether there is an improvement of driving range.&lt;/div&gt;&lt;div class="htmlview paragraph"&gt;Firstly, basic framework of the full vehicle model established in AMESim was introduced. Next, modeling details of individual sub-systems were illustrated respectively. Then, full vehicle energy consumption test was carried out in -7°C ambient condition to check the simulation accuracy. Finally, a variety of battery heating strategies parameterized by heating threshold X and Coefficient of Performance (COP) were investigated to study the effects of improvement of driving range.&lt;/div&gt;&lt;div class="htmlview paragraph"&gt;On the whole, simulation results of energy consumption and driving range are in good agreement with experimental data. In architecture 1, no PTC heating or only PTC heating (COP=1) was considered, the optimum X was found at 10°C, middle of a search interval of [0°C, 20°C]. The corresponding driving range is 237.177km, which is nearly 2km longer than that of base scheme, namely no PTC heating. In architecture 2, which accounts for a virtual heat pump (COP=2), the optimum X was found at 25°C, near the border of specified [0°C, 30°C] search scope. The corresponding driving range is 282.191km, and a range enhancement of 9.64km was acquired compared to the basic scheme of no heating. However, as to the actual architecture that using PTC and/or MWHR, a solely utilization of MWHR was foun to be the optimum, in other words, PTC heating in advance of MWHR has no benefit to the improvement of driving range.&lt;/div&gt;&lt;/div&gt;

Heating performance of a coolant-source heat pump using waste heat from stack and electric devices in fuel cell electric vehicles under cold conditions

Solar Heating and Cooling System with Absorption Chiller and Latent Heat Storage – A Research Project Summary

A lower compression ratio has been demanded for diesel engines in recent years to improve fuel consumption, exhaust emissions and maximum power recently. However, low compression ratio may have combustion instability issues under cold temperature condition, especially just after engine started. As the first step in this study, cold temperature combustion was investigated on the basis of an in-cylinder pressure analysis, and it was found that higher heat release around top dead center, which was mainly attributed to pilot injection, was a key factor in reducing engine speed fluctuation. Three-dimensional computational fluid dynamics simulations were conducted to obtain a better understanding of combustion under cold condition, particularly mixture formation near the glow plug. Specifically, for this purpose, a time-scale interaction combustion model was developed for simulating combustion phenomena. This model was based on a reasonable combustion mode, taking into account the characteristic time scale of chemical reactions and turbulence eddy breakup. In addition, the parameters of the ignition model and computational grids near the glow plug were improved for application to cold start conditions.