The coiling temperature control problem for soft cooling pattern was investigated in this study. It has been found that the abnormal coiling temperature control behavior was caused by the use of incorrect preset value of spray efficiency modifier and non-linearity in the spray efficiency when the cooling pattern was overridden. To solve this problem, a cooling pattern model is hence established. By calculating the ratio of cooling rate for soft cooling pattern, both the spray efficiency modifier as well as the equivalent spray quantity compensation multiplier for cooling pattern override has been derived. The coiling temperature control and model adaptation program was then revised by adding the compensation multiplier in case of cooling pattern override. After the revision of spray efficiency modifier and coiling temperature control program, it was noted that the coiling temperature control of soft cooling pattern was significantly improved.

When machining hardened steel (≥ 45 HRC) with polycrystalline cubic boron nitride (PCBN) tooling, the cutting speeds used produce high temperatures in the primary shear zone, which are sufficient to plasticise the workpiece. The paper initially reviews the effect of workpiece hardness and cutting speed on chip formation, workpiece surface integrity and cutting forces. Equations are detailed for determining the primary shear zone temperature, the proportion of heat conducted into the workpiece and the shear flow stress. Following on from this, experimental work is presented involving the orthogonal machining of AISI H13 hot work die steel with PCBN tooling. Tests were carried out over a range of cutting speeds with workpieces of different hardness, in order to provide cutting force, shear angle, chip morphology and primary shear zone thickness data. The shear flow stress decreased with increasing cutting speed and/or workpiece hardness. With the AISI H13 heat treated to 49±1 HRC, the stress magnitude changed more significantly with cutting speed and the proportion of heat conducted away from the workpiece approached 99% at 200 m/min. Shear localised chips were produced with white unetched layers due to intense heat generation followed by rapid cooling.

This paper presents the design, fabrication approach, and initial results on the development of an active composite fabric comprising a system of energy-efficient micro-miniature vapor-compression heat pumps to form integrated mesoscopic cooler circuits (IMCCs). Wafer-scale microfabrication, traditional volume processes such as injection molding, and new layered fabrication techniques have been combined with a scale-efficient vapor-compression cycle. The resulting IMCC offers significant improvements in cooling efficiency over normal-scale refrigeration. The flexible polymer-based IMCC patches may be interconnected to form distributed fault-tolerant refrigeration circuits for a wide variety of applications. Potential applications include microclimate control for military, space, and fire fighting personnel, on-board/chip cooling of electronic devices, medical applications requiring highly localized and/or efficient temperature control, and automotive comfort control devices.

A steady-state model was developed to predict the performance of the high-pressure side of vapour-compression air-conditioning systems. The model consists of two segments; the compressor model and condenser model. The compressor model consists of a single empirical equation, for reciprocating compressors, operating with R-22, and having a cooling capacity from 2.6 to 3.5 kW. An important advantage of the approach is that the compressor performance indexes are based on operating conditions. The condenser model displays an exact method to determine physical dimensions of heat exchangers, and a simple, accurate manner to calculate the heat transfer variables. The correctness of the condensing temperature is obtained by an iterative procedure, using terms from both the compressor and condenser studies. The feasibility of the proposed model is demonstrated via a comparison with experimental data and a simulation study. Results indicate a good correlation between the mathematical model and its counterparts.

Battelle has developed a mesoscale combustor/evaporator that provides a lightweight and compact source of heating, cooling, or energy generation for both man-portable and stationary applications. The device uses microscale flow channels that increase the available surface area for heat transfer and reduce the fluid boundary layer. These characteristics in turn result in heat fluxes for hydrocarbon/air combustion in excess of 25 W/cm 2 and thermal efficiencies of 80 to 90%. Furthermore, high heat transfer rates allow for short channels and reduced pressure drops. Recent development efforts have focused on obtaining low emissions and improving the combustor/evaporator fabrication process. By using spatially varying stoichiometry inside the combustor, catalyst coated microchannels, and increased coolant temperature, the combustor’s CO and NO x emissions were reduced to below California standards for hot water heaters and boilers. The fabrication process photochemically machines thin metal laminates and then uses diffusion bonding to form a monolithic component. This approach is capable of high fin aspect ratios and can be scaled up for mass production.

Absorption chillers are gaining global acceptance as quality comfort cooling systems. These machines are the central chilling plants and the supply for comfort cooling for many large commercial buildings. Virtually all absorption chillers use lithium bromide (LiBr) and water as the absorption fluids. Water is the refrigerant. Research has shown LiBr to be one of the best absorption working fluids because it has a high affinity for water, releases water vapor at relatively low temperatures, and has a boiling point much higher than that of water. The heart of the chiller is the absorber, where a process of simultaneous heat and mass transfer occurs as the refrigerant water vapor is absorbed into a falling film of aqueous LiBr. The more water vapor absorbed into the falling film, the larger the chiller’s capacity for supporting comfort cooling. Improving the performance of the absorber leads directly to efficiency gains for the chiller. The design of an absorber is very empirical and requires experimental data. Yet design data and correlations are sparse in the open literature. The experimental data available to date have been derived at LiBr concentrations ranging from 0.30 to 0.60 mass fraction. No literature data are readily available for the design operating conditions of 0.62 and 0.64 mass fraction of LiBr and absorber pressures of 0.7 and 1.0 kPa. Experiments were conducted on an internally cooled smooth tube 0.01905 m in outside diameter and 1.53 m in length. Tests were conducted with no heat and mass transfer additive. The data, for testing at 0.62 and 0.64 mass fraction of LiBr, were scaled and correlated into both Nusselt (Nu) and Sherwood (Sh) formulations. The average absolute error in the Nusselt correlation is about ±3.5% of the Nu number reduced from the experimental data. The Sherwood correlation is about ±5% of the reduced Sh data. Data from the open literature were reduced to the authors’ Nu and Sh formulations and were within 5% of the correlations developed in the present study. Hence, this study provides correlations for the complex heat and mass transfer process that is validated against extensive experimental data. The study therefore contains useful information for the design of a vertical column absorber operating with no heat and mass transfer additive.

In the absorption-evaporative cooling refrigerator, the evaporator works with liquid butane and a gaseous ammonia-butane mixture. In order to design such a refrigerator the mixture behavior has to be known. In this paper such behavior is determined first considering an ideal gases mixture and no ammonia in the liquid butane. For this purpose a psychrometric chart for a pressure of 105 kPa is obtained. To validate these assumptions a second model is chosen that considers a certain amount of non-ideality. The selected model is represented by the equations of Peng-Robinson. The results obtained for the equilibrium conditions are compared with the 100% relative humidity of the psychrometric chart. A satisfactory agreement is found.

Optimal shapes and geometries are determined for systems involving liquid and gas coolants. The shape of the channel boundary, channel width, and wall thickness are varied to minimize overall thermal resistance under flow constraints involving pressure drop and pump work. The effect of boundary curvature is studied systematically by employing a parameterized boundary shape that spans from rounded rectangles to ellipses to rounded diamonds. The results indicate that increased channel boundary curvature can decrease the optimal distance between channels, and that the optimal boundary shapes of fully embedded channels can be non-rectangular. In particular, elliptic and nearly elliptic shapes are found to produce equivalent optimal thermal performance as rounded rectangular shapes under practical conditions.

This study involves the experimental verification of a universal heat exchanger accumulator design procedure. A heat exchange accumulator was manufactured according to a mathematical model developed by the authors and installed into a small air conditioning system. Experimental results show that the addition of the heat exchanger accumulator results in a liquid overfeeding operation that replaces the previously utilized direct expansion operation. It provides an improved air conditioning system that has a 7.5% increase in coefficient of performance and a 4.4% increase in refrigerant mass flow rate. A pressure ratio reduction has a positive effect on the compressor performance and life span. Liquid overfeeding increases the cooling capacity of the system by 6.5%. When compared to direct expansion systems, this basic heat exchanger accumulator provides a reduction in cycling losses and power consumption, an increase in suction pressure and an improvement in isentropic compressor efficiency.

Battelle, Pacific Northwest Division (Battelle) and Pacific Northwest National Laboratory 1 (PNNL) are developing a miniature absorption heat pump. Targeted applications include microclimate control ranging from manportable cooling to distributed space conditioning. The miniature absorption heat pump will be sized to provide 350 W t of cooling 2 . A complete manportable cooling system, which will include the microscale heat pump, an air-cooled heat exchanger, batteries, and fuel, is estimated to weigh between 4 and 5 kg. For comparison, alternative systems weigh about 10 kg. Size and weight reductions in the microscale heat pump are possible because the device can take advantage of the high heat and mass transfer rates attainable in microscale structures.

In this paper I present the results of my studies on a new explanation of the vortex (Ranque-Hilsch) tube’s phenomenon. It is new way of understanding this process. The vortex tube was discovered in 1930 by French physicist Georges Ranque. Hilsch was the first American engineer to develop this phenomenon into practical, effective cooling solutions for industrial applications and theoretical modeling and calculations. Currently, the use of conventional vortex pipes is limited in engineering application because of their low thermodynamic efficiencies. Problems associated with these thermal limitation include the separation of gaseous condensate, the separation of liquified air, and more. Still, some technological studies on heat energy generation using new techniques and heat transformation devices should be conducted. This paper addresses the subject of the Ranque-Hilsch vortex tube’s phenomenon explanation based on a vortex-exited oscillation. There is no previous work reported in the literature desdribing the temperature splitting model by wave generating process. The study was motivated by the heating and cooling phenomenon that occurs in the Ranque-Hilsch vortex tube.

Hydrogen has higher flame velocity and smaller quenching distance than hydrocarbon fuels, and is supposed to have special characteristics in combustion process of internal combustion engines. In this research, contributors to thermal efficiency in a hydrogen premixed spark ignition engine were analyzed and compared with methane combustion. Results showed hydrogen combustion had higher cooling loss to combustion chamber wall, and thermal efficiency of hydrogen combustion was mainly dominated by both cooling loss to combustion chamber wall and degree of constant volume combustion.

The thermodynamic effects are demonstrated of integrating steam turbine-based cogeneration systems with absorption chillers. A wide range of realistic extraction steam pressures and coefficient of performance (COP) values of absorption chillers are considered. A simple model of a steam turbine-based cogeneration plant is used for the evaluation of the integrated system. The integrated systems are evaluated based on the ratio of fuel consumption between a base case (one-stage absorption chiller with a COP value of 0.6) and several alternative cases (multi-stage absorption chillers with COP values ranging from 0.6 to 1.5). Two categories of scenarios are considered: (i) cases where the cooling load is fixed; and (ii) cases where the cooling load is fixed and the electrical output for the integrated system is set equal to that for the base case.

This study presents some of the experiences gained during a two year operational period of a decentralized fuel cell cogeneration plant installed in southern Sweden. Various modifications to the system are described, most notably a plume eliminator for the reduction of an undesirable vapor cloud emitted by the original system. Aside from vapor cloud elimination, the plume eliminator allows for more efficient plant operation, as a larger fraction of the system cooling requirements can be shifted to the district heating system. In-field measurements show a 17 to 26% increase in district heat production with use of the plume eliminator, depending upon the season of operation (winter or summer). The study also presents two options for added heat recovery, which are employed in conjunction with the plume eliminator: an air preheater module; and an air preheater/humidifier module. Calculations show that air preheating has a small but measurable impact on heat recovery (an additional 8% gain), while combined air preheating and humidification allows for nearly a 50% increase in district heat production.

The turbulent flow field at the rotor-stator gap entrance of a generator was investigated numerically. Predictions of the fluid dynamics characteristics for the present problem were made by adjusting boundary pressure conditions to match the prescribed flowrate allocation. The velocity field and pressure distribution at the rotor-stator gap entrance were presented. The mean values of pressure and velocity, obtained by integrating the local values across the flow cross-sectional lines, were applied to calculate pressure loss coefficient ß at the gap entrance. Results show that because of the complex geometry at the air gap entrance and flow splits through the stator cooling ducts, the display of ß is rather complicated. Rotating body windage losses for the rotor and retaining rings were determined from calculated friction factors on these surfaces.

The RELAP5 Mod 3.1 computer code has been utilized to study the causes of exhaust line rupture disk actuation that occurred without indication of overpressure conditions. A series of cases have been investigated to determine the conditions in the RCIC upstream steam supply as well as the exhaust piping that would lead to dynamic behavior capable of causing exhaust system rupture disk failure. It has been demonstrated that the presence of moisture in the turbine and/or its immediate exhaust piping, are necessary to achieve the pressures necessary to fail the rupture disk. The upstream steam supply conditions can significantly influence the transient, particularly if saturated water is able to enter the turbine. Saturated water ingestion to the turbine can lead to significantly higher exhaust pressure behavior. The upstream supply conditions cannot, however, result in rupture disk failure if there is not water present in the turbine/exhaust line at startup. This paper discusses the modeling methods, as well as the results obtained from the computer simulation.

This paper addresses the impact of adding insulated extensions at the entrance of a parallel-plate channel in which the plates receive a uniform heat flux and a natural convection air flow is responsible for the cooling. The full elliptic conservation equations are solved numerically in a composite I-type computational domain. It was found that the wall temperatures increase when the channel extensions are appended at the inlet. The pertinent results are reported in terms of maximum wall temperatures, induced mass flow rates, as well as velocity, pressure and temperature profiles of the fluid.

A new type of multilayer thermionic coolers with varying barrier heights is proposed in this article. Based upon the assumption of ballistic electrons in the filters and thermalized electrons in the bases, we analyzed the energy balance at each stage. As the heat flux increases at later stages, the barrier height should also increase. The optimum structure is obtained by a trial-and-error method. Calculation results show that the coefficient of performance does not change significantly with the number of stages of the thermionic cooler. The heterojunction structure with varying barrier heights have a slightly higher COP than the one with a fixed barrier height.

Solidified high level radioactive wastes generate decay heat that must be taken into account during interim storage in engineered facilities prior to geological disposal. The continual heat generation within the canisters necessitates reliable heat removal to avoid overheating of the stored material and the surrounding safety barriers. This paper is concerned with the modelling and computation of heat transfer in one of the storage cells, based on the conceptual design study for natural convection cooled high level radioactive waste storage. All internal features of the storage cell have been explicitly modelled to analyse the internal heat transfer process by conduction and natural convection coupled with thermal radiation. One of the major objectives of the current study was to assess the contribution of radiation heat transfer in altering temperature profiles in the storage cell. Furthermore the model has been used to predict the effects of surface radiative properties, canister filling material conductivities and waste loading on the temperature and velocity fields. A variation in the enclosed air gap width and also cooling air channel width has also been performed to see their potential effect on temperature profiles of the storage cell.

A new idea of a particle handling system is proposed in this paper consisting of a network of channels and a matrix of mechanical gates for fluids. The device consists of a silicon chip encapsulated by two glass chips. A free standing silicone membrane with a thickness of only two microns is used to reduce the cross sections of the channels. The selected cross section of 30 × 7 μm allows to handle particles with sizes ranging from the sub micron scale to a few microns. We could show that the flow of these particles in the channels can be controlled by actuating the valves and monitored with a video microscope. The density of valves is 600 valves / square inch in our first prototype. The second prototype with a valve density of 100 valves / square inch also includes channels for cooling of the device.