Design of New Power Source Based on Micro-SOFC for Mobile Electronic Devices

Introduction. The tasks of increasing energy saving in heating systems for passenger cars of diesel trains are currently relevant. As an alternative source of energy for these systems, the possibility of using the waste heat of the diesel locomotive engine is analysed.Materials and methods. The article provides an analysis of the engine waste heat sources, cooling water and exhaust gases. A schematic diagram of exhaust gas heat exchanger for its use in the heating system of passenger cars has been deve loped. As a possible heat-exchange surface of the waste heat exchanger, plate-ribbed, coiled and tube surfaces with longitudinal boundary layer turbulators are proposed. The required area of this surface for the maximum power of the heating system for a passenger train is determined.Results. The article shows the possibility of using engine exhaust heat in the heating system of a 15-car passenger train without involving third-party energy sources.Discussion and conclusion. The obtained results demonstrate a sufficient potential for increasing the efficiency of using the diesel engine fuel energy when utilising its waste heat for the heating system of passenger cars. The selection of a waste heat exchanger is justified based on a performance of 50 % of the peak load on the heating system at the middle position of the controller.

<div class="section abstract"><div class="htmlview paragraph">The success of improved fuel economy is the proper integration of thermal management components which are appropriately performed to reduce friction and wasted energy. The thermal management systems of vehicle are able to balance the multiple needs such as heating, cooling, or appropriate operation within specified temperature ranges of propulsion systems. Since the propulsion systems of vehicle have changed from a single energy source based on conventional internal combustion engine to hybrid system including more electrical system such as full type of hybrid electric vehicle or plug-in hybrid electric vehicles, a new transition associated with vehicle thermal management arises. More efficient thermal management systems are required to improve the fuel economy in the hybrid electric vehicles because of the driving of electric traction motor and the increase of engine off time. The decrease of engine operation time may not sustain the proper temperature ranges of engine and gearbox. As an engine starts at low ambient temperature, heat from the wasted heat of exhausted gas can be supplied not only to cabin heater, but also to engine and gearbox at initial warm-up.</div><div class="htmlview paragraph">To practically apply recent thermal management technologies in commercial use, improved performance for the low energy density per cost in a viable vehicle package is necessary in general. This research describes the one of cost effective thermal management solutions recovering exhaust gas heat exchanging system with coolant and gear box oil simultaneously. The previous type of recovering the exhaust heat is to exchange the heat between the coolant and the exhaust gas to increase the temperature of the engine coolant, thereby reducing the friction and improving the fuel efficiency. However, the reduction in engine friction loss and improvement of fuel economy remains low due to the short period of exchanging heat between exhaust gas and coolant. It is more advantageous to increase the temperature of the engine oil or gear box oil rather than to increase the coolant temperature. Accordingly, the developed exhaust heat recovery device which performs integral heat exchange of the exhaust gas heat of engine increases the temperature of the coolant and the gear box oil, thereby reducing friction loss and improving fuel economy. The experimental result of this system improved 2.5% of fuel economy at UDDS drive cycles.</div></div>

The objectives of this study were to evaluate physiological responses to heat stress of Holstein heifers carrying the SLICK1 allele of the PRLR, i.e., the slick mutation. Slick and non-slick females were produced in central CA (n = 3 farms) and south FL (n = 3 farms) by inseminating cows with semen from two heterozygous slick Holstein sires. In July 2020, a subgroup of heifers of both genotypes (slick=93; non-slick=110) and two age groups (Group 1: 6–8 months old; n = 131; Group 2: 9–51 days old; n = 72) in both states were evaluated for rectal temperature (RT), surface temperature (ST) and sweating rate (SR). Dry bulb temperature, relative humidity and dew point were recorded every 15 min during testing for temperature humidity index (THI) calculation. Statistical models included the effects of genotype, state, farm within state, group, sire, THI, and interactions. Significant effects were considered as those with P < 0.05. Although the THI in CA was lower than FL (80 ± 0.1 vs 84 ± 0.2; P < 0.01), both were above 77 (estimated heat stress threshold for young animals). Slick heifers raised in FL had lower RT compared to non-slick siblings (39.6 ± 0.1 vs 40.1 ±0.1; genotype P < 0.01); this difference was not observed in CA (39.1 ± 0.04 vs 39.1 ± 0.05; genotype P = 0.5; state x genotype P < 0.01). In both states, slick heifers tended to have lower ST (34.7 ± 0.2 vs 35.1 ± 0.2; P = 0.07); CA heifers had lower RT and ST and higher SR (P < 0.01) regardless of genotype. Current results show that presence of the SLICK1 allele can improve the ability of Holstein heifers to regulate body temperature, particularly in high humidity conditions. Next steps will include analysis of performance as study animals enter the reproductive phase. Funding sources: Holstein Association USA and L.E. “Red” Larson Endowment.

Heat exchangers transfer heat between two or more media. They exist in a large variety of types in the chemical and power industries, in buildings and vehicles. Typical faults in these heat exchangers are leaks, e.g. by corrosion and the contamination by dirt and dissolved or suspended matter. The growth of deposits is called fouling and leads to a reduction of heat transfer. Therefore heat exchangers are usually designed with excess heat transfer surfaces of about 35% average, [10.16]. This excess design increases costs, space and weight. Remedies against fouling are chemical or mechanical mitigation techniques like filtration, additives, higher velocities, lower surface temperatures, polished surfaces. However, fouling cannot usually be avoided completely and therefore periodic cleaning will still be necessary. For more details see, e.g. [10.19], part Oc 1 and [10.17]. The detection of leaks in heat exchangers may be based on mass balances and methods described in Chapter 7. Fouling increases mainly the heat transfer coefficients, respectively the heat transfer resistance and to a minor extent the flow resistance of the media. The following sections describe some methods to detect changes of the heat transfer and some experimental results for steam-heated tubular heat exchangers with linear and parameter variable models.

The influence of inner topology of exhaust heat exchanger and thermoelectric module distribution on the performance of automotive thermoelectric generator

The Maisotsenko Open Cycle combines the thermodynamic processes of heat exchange and evaporative cooling in a unique indirect evaporative cooler resulting in product temperatures that approach the dew point temperature, (not the wet bulb temperature) of the working gas. It is an open thermodynamic cycle utilizing several thermodynamic processes that cools a product fluid with a liquid evaporating into a gas, generally water evaporating into air from the atmosphere and returns it to the atmosphere. It is a new cycle as no other cycle can be diagramed in the same way on the psychrometric chart of a gas. In a gas turbine, the gas is air and evaporate is water. An atmospheric pressure heat and mass exchanger operating with the Maisotsenko Cycle can be used to cool compressor inlet air below the wet bulb temperature. In a high-pressure heat and mass exchanger the cycle can create a compressed air saturator using heat from the turbine exhaust gases and also cools water for heat recovery in a compressor inter-cooler. The same saturator will humidify and/or superheat the compressed air before entering a combustor to the amount desired. From a practical stand point the limit of humidification of the compressed air is the amount of heat available at a temperature above its dew point temperature from the exhaust gas and/or intercompressor coolers. The amount of superheating or humidifying of the compressed air is easily controlled and changed during operation allowing added power, or greater efficiency, (60% overall thermal efficiency) quickly and easily. The equipment uses existing shell and tube heat exchanger or plate heat exchangers technologies. There are many other benefits ranging from lower NOx to greatly reduced equipment cost compared to any other power cycle enhancement systems.

Solid oxide electrolysis (SOEC) systems have the potential to produce hydrogen and oxygen propellant from lunar ice found in the permanently shadowed cream on the moon. Because SOEC systems electrolyze steam instead of liquid water as in more conventional alkaline and proton-exchange membrane electrolysis systems, they require lower stack voltages for thermal-neutral operation (about 1.29 V/cell vs. 1.48 V/cell for liquid-fed cells) and thus can have lower stack specific energy as defined by stack power requirements per kg of hydrogen produced. However, at a system level, power requirements in a remote lunar setting for vaporizing the steam and flowing it through the stack increase system-level power demands such that the advantages of the SOEC system are reduced due to the balance of plant loads contributing as much as 20 to 25% of the system energy at 800 deg. C. Our team at Mines collaborated with our partners at OxEon Energy to demonstrate an SOEC system with a stack operating temperature of 800 deg. C that demonstrated an overall system-level specific energy just below 50 kWh electric per kg of hydrogen. That study and a supporting model validation study provided a basis for showing the viability for high-temperature SOEC to be scaled-up for lunar production of hydrogen and oxygen propellant for propulsion. The current study builds on that previous work by exploring the impact of SOEC stack temperature on both the stack and balance of plant power requirements. This study explores the trade-offs between reduced balance of plant parasitics and increased stack mass with lower SOEC operating temperatures and explores the advantages of higher conducting mixed-ionic-electronic conducting electrolytes with electron blocking layers to increase current densities at lower temperatures.This study was performed using stack and balance of plant models that have been calibrated in the lab-scale demonstration of an SOEC system with an electrically driven steam generator, a scroll-compressor for driving the steam flow, and cathode and anode exhaust recuperators for heat recovery to the stack inlet steam flow. The system also includes H2 drying from the SOEC cathode exhaust by heat exchange with the incoming water stream. The current study looks updates the previous model by replacing the compressor with a higher pressure steam generator and an expansion valve that allows the operation of the system without the parasitic loads of a compressor. In the current study, three different electrolytes traditional yttrium-stabilized zirconia (YSZ), higher conductivity scandium-stabilized zirconia (ScSZ), and mixed ionic-electronic conducting gadolinium-doped ceria (GDC) with a YSZ blocking layer. The GDC bilayer electrolyte cells have the highest conductivity and allow for reasonable hydrogen production at operating temperatures below 700 deg. C. The results show that the lower operating temperatures enabled by the GDC bilayer electrolyte and by the ScSZ electrolytes not only reduce the system mass with smaller heat exchangers and thermal insulation, but also lower requirements for steam generation by enabling more heat recovery in the steam generator. The impact of stack operating temperatures on the feasibility of scaling up a lunar-deployed SOEC system to produce more than 1 kg/h are presented to further emphasize the feasibility of SOEC systems as part of a lunar propellant production facility.

Developing an effective method of reducing nitrogen oxide emissions is an important goal in diesel engine research. The use of cooled exhaust gas recirculation has been considered one of the most effective techniques of reducing nitrogen oxide. However, since the combustion characteristics in a diesel engine involves high temperature and load, the amount of particulate matter emission tends to increase, and there is a trade-off between the amount of nitrogen oxide and particulate matter emissions. In the present study, engine dynamometer experiments are performed to investigate the effects of particulate matter fouling on the heat exchange characteristics of wave fin type exhaust gas recirculation coolers that have four cases of two wave pitch and three fin pitch lengths. To optimize the fin and wave pitches of the EGR cooler, the exhaust gas temperature, pressure drop and heat exchange effectiveness are compared. The experimental results show that the exhaust gas recirculation cooler with a fin pitch of 3.6 mm and a wave pitch of 8.8 mm exhibits better heat exchange characteristics and smaller particulate matter fouling effect than the other coolers.

This paper entails an empirical and computational assessment of the air flow field in the close proximity of a vertically positioned radiant cooling panel. This radiant cooling solution differs from the conventional large-area radiant cooling systems (e.g., ceiling panels). It involves rather small-sized vertical panels positioned close to occupants. Moreover, the panels are designed so as to manage potential surface condensation of water vapor via integrated drainage elements. Hence, the panels can be operated with relatively low surface temperatures. The low panel surface temperature and its proximity to the occupants are intended to compensate for the potential lower cooling power due to the relatively small panel size. In this paper, we specifically explore the air flow field close to the local radiant cooling panel via laboratory measurements and CFD (Computational Fluid Dynamics). Thus, possible issues regarding discomfort due to draft and turbulence risk close to the radiant panel can be examined. To this end, a prototypical local radiant cooling panel was installed in a mock-up office room of a laboratory. During the experiments, the air flow speed was measured and simulated at several heights (between 10 and 110 cm from the floor) and distances (ranging from 1 to 50 cm from the radiant panel). The results allow for the evaluation of the draft discomfort risk as well as the reliability of CFD in reproduction of the measurement results. A further step involved the numeric analysis of the effect of the human model on the air flow patter.

An increase in the fuel efficiency of small-sized gas turbine engines can be achieved by regenerating the heat of the turbine exhaust gases. A rational layout solution in this case is a turboshaft scheme, where the effective power is generated on the shaft of a free turbine, and the turbine exhaust gases are released into the environment without doing useful work. When creating a turboshaft engine with heat recovery, the concept of developing engine family on the base of unified gas-generator was considered. The concept involves the development of a modular system, where the addition or exclusion of individual large units allows changing the type of engine at minimal cost. The article presents the layout solution of a small-sized turboshaft gas turbine engine with heat recovery, developed on the basis of a unified gas-generator and using a gearbox to transfer effective power to a propeller or a rotor. A plate heat exchanger module with a corrugated heat exchange surface for a small-sized turboshaft gas turbine engine has been designed. The heat exchange matrix was developed using a complex techniques of computer-aided design, calculation and manufacture of plate heat exchangers. Some design features of high-temperature plate heat exchangers are identified, the most important of which is the non-uniformity of temperature fields in the heat exchange matrix. Taking into account the non-uniformity of temperature fields, the heat exchanger module is a collapsible structure allowing the replacement of the heat exchange matrix and providing compensation for thermal expansion of the heat exchanger elements. The designed plate heat exchanger module for a small turboshaft gas turbine engine will be manufactured and tested on the bench

Influence of exhaust gas heating and L/D ratios on the discharge efficiencies for an activated carbon natural gas storage system

The automobile industry is in a constant pursuit to improve the fuel economy of vehicles. The internal combustion engine is inefficient due to its inherent irreversibility. Around 30% of the combustion energy is lost in the form of heat with the exhaust gasses. If this lost energy is recovered and utilized, then it will improve the overall fuel economy of the vehicle. Herein, a waste heat recovery concept is presented to recover heat from exhaust gasses in a heavy commercial vehicle. Two exhaust gas heat exchangers are conceptualized and their performances are compared. A novel idea of immersing thermoelectric modules in coolant is proposed instead of using a separate cooling block or channel. The thermal performance is evaluated considering transformer oil as coolant instead of commonly used engine coolant. The performance of two heat exchangers one having a parallel flat plate fin core and the other having a pin fin core configuration is investigated. The effect of coolant volume flow rate and exhaust gas mass flow rate also is analyzed.

The dysregulation in heat balance, the main cause of exertional heat stroke, occurs not only in midsummer but also in the cold season. Possible causes of this are a reduction in convection and evaporation due to tailwinds and an acceleration of radiant heat inflow. Although the amount of radiant heat that reaches the surface can be estimated, the actual amount of heat that flows into the body cannot be specified yet. This paper made an experimental attempt at this. A device is made up of a temperature controllable heat sink and heat flow detector, which keeps the surface temperature constant and has a heat exchange coefficient comparable to that of the human body surface. The output of this device (total heat exchange) was divided into radiant heat exchange and other heat exchange using a standard radiant heat calibrator, Leslie cube. A phenomenon, in which a wet surface while the surface temperature was low absorbed larger heat than that of the dry surface, was found. And authors named this "hidden heat inflow". As a result of multiple regression analyses, both radiant heat exchange and other heat exchanges are closely related to the surface temperature, and the maximum difference in total heat exchange during the experiment reached 200kcal/m2/h. It has been suggested that this phenomenon may also occur on the surface of human skin. One of the causes of this "hidden heat inflow" is considered to be the decrease in evaporative cooling due to the decrease in surface temperature. However, this alone cannot explain all of the phenomena, so water vapor aggregation may also be involved. A "hidden heat inflow" as a sufficient heat source for exertional heat stroke or collapse during a marathon race on a cold day was evidenced experimentally.

Although the U-value of glazing has improved significantly in the last decades, the thermal transmittance of windows remains relatively high compared to opaque elements of the thermal shell. Consequently, glazing has a relatively low interior surface temperature in the heating season, which can cause thermal discomfort. A novel heated glass element has been developed, allowing for the control of its interior surface temperature. In-situ measurements were conducted on a heated glass element, with the objective to (i) characterize its thermal behaviour, (ii) assess its thermal performance and (iii) to assess its impact on thermal comfort. The examination of heating-up and cooling-down curves of the heated glass element revealed that cooling-down is a slower process (τ2 of 100 – 145 minutes) than heating-up (τ2 of 70-85 minutes). In terms of thermal performance, it is shown that most of the heat provided by the heated glass element is effectively directed towards the room, rather than lost to the outdoor environment. The efficiency depends on the temperature difference between interior glass surface and the room, with efficiencies of 58 – 65% reached at surface temperatures of 23 - 25 °C, and efficiencies of 90% reached at surface temperatures of 39 – 43 °C. Comparative measurements of thermal comfort in a room with the heated glazing, and in a room with conventional triple glazing show an improvement in operative temperature.

Modelling and optimization of a forced convection heat exchanger for Mars waste heat rejection for power cycle and cryocooling applications