Specific Mass Flow Rate Research Articles

Design analysis of corrugated and flat plate solar air heaters

A detailed theoretical parametec analysis has been made on corrugated and flat plate solar air heaters of five differentconfigurations. The analysis involves investigating the effects of the air flow velocities (or the air channel depths) on the air temperatureincrement, the system efficiency and the pressure drop experienced by the flowing air for different air channel lengths and different specific mass flow rates of air. The design analysis and the curves discussed in the article are intended to enable a designer to construct economical and efficient solar air heaters with technically logical air passage dimensions.

Forced convective boiling in high pressure parallel flow in tube bundles

A comparison between the correlations usually proposed for the evaluation of boiling heat transfer coefficients outside tube bundles in high pressure conditions and experimental data (600 points) has been performed. Underpredictions of the correlations in the range of 30–40% have been found. Using the same structure as the Chen correlation but with different specifications of the Fand S corrective factors, a new correlation is proposed, whose application predicts 80% of the data with a mean error of 13%, and 90% of the data with a mean error of 30% in the following ranges: pressure, 35–90 bar; specific mass flowrate, 180–1800 kg/m 2s; heat flux, 30–300 kW/m 2; quality, 10–90‰.

Ultrasonic measurements of solid propellant burning rates in nozzleless rocket motors

Burning rates at several axial locations along the grain port of subscale nozzleless motors were measured by ultrasonic transducers that detect the instantaneous web thickness of the propellant. Two experimental devices were used for this: an axisymmetric nozzleless motor loaded with a metallized composite propellant and a twodimensional window nozzleless setup loaded with a nonmetallized composite propellant. The ultrasonic transducers give an estimate of the grain deflection during motor pressurization. In both setups, the nocrossflow burning rate measured in the head-end region agrees with standard strand burner data, and high erosive burning rates are found in the aft-end region. These erosive burning data have been represented in a format that includes the main experimental variables: port radius or channel width, no-crossflow burning rate, and mean crossflow velocity. The results reveal that the generally observed trends of threshold specific mass flow rate, no-crossflow burning rate sensitivity, and scale dependence are also demonstrated in nozzleless motors.

Simultaneous measurement of the stagnation temperature and specific mass flow rate in a hypersonic gas flow

The procedure and results of simultaneous measurement of the stagnation temperature and specific mass flow of gas in a hypersonic flow by means of heated-chamber impact tubes is discussed. The construction of the tubes is described.

Transient critical heat flux in loss-of-flow-accidents (L.O.F.A.)

Loss of flow transients with reference to L.O.F. accidents in nuclear reactor cores have been systematically studied employing freon 12 as coolant. Two pressures (with reference to BWR and PWR characteristic liquid to vapour densities ratios), three periods of the coast-down flow transients during the simulated pump trips, and different specific mass flow rates have been investigated. The uniformly heated channel ( L = 200 cm, D = 0.75 cm), instrumented with wall thermocouples and inlet to outlet differential pressure enabled recording of the following transients, inlet specific mass flowrate, inlet pressure, inlet to outlet Δp, inlet fluid temperature, outlet wall temperature, outlet bulk temperature. Through the wall temperature being close to the outlet it is possible to detect the onset of DNB and hence the time to DNB from the beginning of the flow transient. All the experimental runs (105) have been systematically compared with the G.E. (PEPE) code with the introduction of a CNEN DNB freon correlation. The results enable a series of conclusions which are extensively shown in the paper.

Heat transfer crisis data with steam-water mixture in a sixteen rod bundle

The experimental data obtained under the PELCO program on heat transfer crisis (54 point) with vertical upward flow of boiling water in a sixteen rod square bundle are presented. The experiments were carried out with the CISE IETI-3 heat transfer facility under the following conditions: geometry: 1. (1) square array of sixteen rods 2. (2) rod dia.: 1 51 cm 3. (3) overall heated length: 270 cm radial power distribution: uniform axial power distribution: two steps ( φ upstream = 2 0 φ downstream; L upstream = 104 cm) specific mass flowrate: 70–160 g/cm 2s (seven values) subcooled water at inlet: (5–75°C subcooling) test section average pressure: 69 kg/cm 2 abs. A brief description both of the test element design and of the experimental plant is given. A short discussion of critical power results and a comparison with the predictions of some of the available correlations are also reported.

Measurement of the Effect of Twisted Tapes on the Forced-Convection Heat Transfer and Burnout in Heat Exchangers

Very promising results with the insertion of twisted tapes in tubular heat exchangers have suggested performance of experiments under more interesting conditions, i.e., at higher pressures (50 atm) with exchangers of larger dimensions (200 cm in length and 1-cm i.d.).The results show a great increase in the forced-convection heat transfer coefficient ranging from 100 to 150% at specific mass flow rates of 70 to 100 g/(cm2 sec).The law of dependence of the Nusselt number on the Reynolds number varies with an exponent unity instead of 0.8. The burnout thermal power increases by 30 to 50%; correspondingly, the burnout qualities increase from 60 to 90%, thus drastically reducing the post-burnout length. Furthermore, within this length there are no characteristic, dangerous temperature oscillations.The present results, together with others cited in the referenced literature, constitute a basis for improvement of the subcritical once-through heat exchangers for pressurized-water and liquid metal fast breeder reactor power plants.