Specific Heat Input Research Articles

Experimental investigations on desiccant wheels

Experimental investigations on several commercially available and newly fabricated rotors are conducted in two different laboratories to evaluate performance trends. Experimental uncertainties are analysed and the parameters determining the rotor performance are investigated. It is found that the optimal rotation speed is lower for lithium chloride or compound rotors than for silica gel rotors. Higher regeneration air temperatures lead to higher dehumidification potentials at almost equal dehumidification efficiencies, but with increasing regeneration specific heat input and enthalpy changes of the process air. The influence of the regeneration air humidity was also notable and low relative humidities increase the dehumidification potential. Finally, the measurements show that rising water content in the ambient air causes the dehumidification capacity to rise, while the dehumidification efficiency is not much affected and both specific regeneration heat input and latent heat change of the process air decrease. For desiccant cooling applications in humid climates this is a positive trend.

Experimental Investigation of a Pulsating Heat Pipe Using Ferrofluid (Magnetic Nanofluid)

In this work, a four-turn pulsating heat pipe (PHP) is fabricated and tested experimentally. The novelty of the present PHP is the capability to obtain various thermal performances at a specific heat input by changing the magnetic field. The effects of working fluid (water and ferrofluid), charging ratio (40% and 70%), heat input (35, 45, 55, 65, 75, and 85 W), orientation (horizontal and vertical heat mode), ferrofluid volumetric concentration (2.5% and 7%), and magnetic field on the thermal performance of PHPs are investigated. The results showed that applying the magnetic field on the water-based ferrofluid reduced the thermal resistance of PHP in all orientations. In the presence of a magnetic field, the best thermal performance was achieved at the higher charging ratios (70%) in all orientations.

Effect of welding parameters on morphology and mechanical properties of Ti–6Al–4V laser beam welded butt joints

The influence of welding speed and laser power on weld quality of 1.6 mm thick Ti − 6Al − 4V sheets autogenously laser beam welded in butt configuration using a Nd-YAG laser was studied. The joint quality was characterized in terms of weld morphology, microstructure and mechanical properties. An underfill defect, controlling the whole weld geometry, was observed both at the weld face and root surface. In dependence of the specific heat input, this defect showed a maximum, which separates two different welding regimes: keyhole welding, at low heat input, and a welding regime where heat conduction around the keyhole is predominant, at high heat input. Influence of the underfill radius on the weld fatigue life was also assessed.

Soil water flux density measurements near 1 cm d−1 using an improved heat pulse probe design

The heat pulse probe (HPP) technique has been successfully applied for estimating water flux density (WFD). Estimates of WFD have been limited to values greater than 10 cm d−1, except for two recent studies with lower detection limits of 2.4 and 5.6 cm d−1. Although satisfactory for saturated soils, it is recognized that current HPP capabilities are limited for applications in the vadose zone, where WFD values are generally below 1 cm d−1. Since numerical sensitivity analysis has shown that large heater needle diameters may increase HPP capabilities in the lower flux density range, a HPP with a 4‐mm‐diameter heater needle was developed and tested. WFD values were obtained by fitting temperature data to the analytical solution for a pulsed cylindrical heat source of infinite length. Effective heater‐thermistor distance and soil thermal diffusivity values were determined for specific heat input scenarios with zero WFD, prior to imposing water flow across the HPP needles. We showed excellent results in the range of 1–10 cm d−1 and satisfactory results in the range of 10–1000 cm d−1.

The heating of the solar corona

The heating of the solar corona has been a fundamental astrophysical issue for over sixty years. Over the last decade in particular, space-based solar observatories (Yohkoh, SOHO and TRACE) have revealed the complex and often subtle magnetic-field and plasma interactions throughout the solar atmosphere in unprecedented detail. It is now established that any energy release mechanism is magnetic in origin - the challenge posed is to determine what specific heat input is dominating in a given coronal feature throughout the solar cycle. This review outlines a range of possible magnetohydrodynamic (MHD) coronal heating theories, including MHD wave dissipation and MHD reconnection as well as the accumulating observational evidence for quasi-periodic oscillations and small-scale energy bursts occurring in the corona. Also, we describe current attempts to interpret plasma temperature, density and velocity diagnostics in the light of specific localised energy release. The progress in these investigations expected from future solar missions (Solar-B, STEREO, SDO and Solar Orbiter) is also assessed.

Radial distribution of specific heat input in the column of a stabilised plasma arc

When using CO 2 as a plasma-forming medium, large losses of energy for dissociation change the nature of the radial distribution of specific thermal power. The more uniform distribution of specific thermal power in the central zone of the column of the stabilised plasma arc reduces the effect of the technological disruptions on the melting processes of the filler and parent metal

A Study of Hot Machining : A New Heating Method by Friction

The heating method used in hot machining affects the machinability, machining accuracy, protection for machine tool, cutting tool, and operator. Heating method used hitherto are flame heating, resistance heating, arc heating, induction heating, radiant heating, and others. These heating methods are advantageous in some respects, but require large heating apparatus. Some of them require protection for operator and some are high in initial and running costs. In this paper, a new heating method using friction between the work and shoes was presented. Experimental results showed that the friction heating method was very efficient for the purpose of heating the work materials. It produced a large amount of specific heat input. Both initial and running costs for it were low. Operating this heating apparatus was found safe.

ジルコニウムおよびジルカロイ-2合金の電子ビーム溶接に関する研究

A high-voltage electrcn-beam welding machine with a maximum beam power of 1.5 kw (50 kV, 30 mA) has been operated in the Japan National Research Institute for Metals since July 1960. With this equipment, the characteristics of bead penetration and welded joints of Zirconium and Zircaloy-2, namely, microstructure, hardness, tensile and bending properties and corrosion resistance against high temperature, high pressure water studied as compared with the case of TIG welding, and the following conclusions were obtained :(1) It is possible to make a butt-joint weld at a high welding speed such as 40 to 100cm/min up to about 2.0 mm thickness of sheet.(2) Relationship between specific weld heat input and ratio of bead penetration-to-width is given by following equation. w/p X 100=76 log H-45(3) About three times the specific weld heat input of electron beam welding is necessary for TIG welding to give the same bead penetration.(4) To make a smooth and not-burn - through welding bead, it may be supposed that a low voltage type power source should be preferred type, especially, for a thin sheet.(5) No evidence has been found to substantiate the occurrence of a change in oxygen and nitrogen composition due to this welding process.(6) Metallography, hardness, mechanical-property evaluations and corrosion tests have revealed satisfactory properties in Zirconium and Zircaloy-2 wleded joints by this welding process.