In the heatexchangers of the type of pipes with annular space, there are many cases of heat transfer of the entry length in which heat exchange begins at the entrance of pipes, and especially this is an important problem in the case of heat transfer of the atomic reactors. The experiments were performed, in which cases water from down to upward through the pipes with annular space was heated from the inner pipe.

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In the previous paper the writers published a report on the experimental results on the heat transfer coefficients of inclined circular cylinders of finite length due to the free convection in which the heat losses from their end surfaces were excepted. In this investigation, the heat losses from the end surfaces of a circular cylinder, which are located horizontally upward or downward in the still air, have been measured by "the temperature boundary layer method" together with the usual "heat quantity method" in either case where the cylindrical surface is heated or not. From the experimental results, the local and the mean heat transfer coefficients of each surface are evaluated and expressed by empirical formulae which show remarkable difference from the case of horizontal plate.

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We have obtained the heat transmitting tubes of a new type which are easy to make and superior in point or heat transmission. These new tubes are the ones equipped with one or two plane axial fins perpendicularly on the outer surface of circular tubes. Our researches were carried out measuring the heat quantity absorbed in water, flowing through the tubes which were held perpendicularly to the flow of air of 80°C. The main results of our researches are as follows : (1) The characteristic of the tube having two fins, stretching in axial direction on its front surface is influenced by air velocity, the angle 2θ between the two fins, holding at the center of tube and fin height. Among these factors the second must be attended especially. The tubes having the fins of proper angle (2θ=20°∼60°) and proper height on its front surface are most useful. (2) The tube having an axial fin of larger height on its front surface against the air flow is also useful.

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Engine experiments and a new conversion formula of indicated mean effective pressure are described in the present paper. The formula holds good at any constant fuel-"dry air" ratio, and agrees with the experimental results within ±1.5% errors, and is especially new at the humidity conversion term, which is better in accuracy than the well-known Brooks-Garlock relation in the cases of exceptionally high vapour-tension as 100 mmHg. The formula stands upon the fo11owing two assumptions, which hold practically true with experimental results : (1) Indicated thermal efficiency should be a function of fue1-"dry air" ratio, (2) Suction air mass shou1d be proportiona1 to a function of fuel-"dry air" ratio and to the square root of the product of atmospheric pressure and density.

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In order to investigate the fundamental phenomena in the free piston gas generator, we have reconstructed the Junkers type free piston air compressor into a gas generator of an inward compression type. The design data are as follows : [table] In the present paper, the design method, the constructional details and the performance of the test running are described.

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As the existing formula for the total pressure drop ΔP in the gas turbine combustor, [numerical formula] includes the total pressure drop ΔP_M due to the momentum change of the gas flow, the physical meaning of the resistance coefficient C₂ becomes doubtful. Therefore, the authers tried to devide ΔP into the net pressure drop δP due to the pure resistance and the pressure drop ΔP_M due to the momentum change in the air flow accompanying combustion as follows : [numerical formula] and [numerical formula] where P=the total press., p=static press., γ=the specific weight of the air or the gas, ν=the mean velocity of flow, T=the temp. of the air or the gas, and suffix 1=the inlet, 2=the outlet, m=the adequate mean position, assuming that the combustor provides pipes of equal cross sectional areas both at the inlet and the outlet. The values of resistance coefficients C_γ1, C_γ2 and C_γm are determined experimentally with various types of heated coils, throttle plates and mixing plate, using the electric heater instead of the combustion of fuels to get higher accuracy in the measurement. From these experiments, it can be concluded that the total pressure drop ΔP of the heated gas can be estimated from the resistance coefficient C_γ0 of the cold state with [numerical formula] if coefficients α, β are properly chosen, without measuring the troublesome mean total pressure drops at all points of the cross section of the outlet pipe. Or, the properties of resistances can be analyzed from the values of α and β, when the total pressure drop ΔP has been measured.

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As we found that the dripping of liquid from the end of a tube with small diameter accompanied no satellite drop, we tried to produce a plenty of uniform drops by means of rotating nozzles, checking the results with theoretical considerations. The chief results obtained are as follows : (1) If the coefficient of the outer diameter C_D2, defined by [numerical formula] (D₂=the outer diameter of the tube, σ=the surface tension and γ=the specific weight of the liquid), is less than 0.4, uniform drops can be produced. (2) When the flow rate q is small, the diameter of drop attains the maximum value d_max which is given by the simultaneous equations [numerical formula] where R₁=the radius from the center to the tip of rotating nozzle, n rpm=the rotational speed and C_w=the coefficient of the drop weight. The functional form of f in (2) is given in the previous paper⁽¹⁾. (3) The diameter of drop decreases with the flow rate from d_max to its minimum value d_min, until the critical rauge is reached, where the mode of flow changes from the dripping to the smooth laminar flow. The value of d_min can be determined from equations (1)∼(3), if we only substitute the value of internal diameter D₁ of the tube to the outer diameter D₂. (1) Tech.Reb.Tohoku Univ.19, 2 (1955), 135.

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In order to measure the time-rate and the integrated amount of gas flow, the present authors tried to combine the by-pass method with the ordinary orifice or nozzle method. They put a standard nozzle in the main flow in order to measure the time-rate of the main flow and tapped two holes, one in front of and the other behind the nozzle, respectively, and then connected these holes to a gasmeter of small capacity by tubes so that minute part of the main flow gas might flow along this by-pass. They throttled the by-pass flow by either orifices or nozzles both at its entrance and exit. The following conclusions from our experiments with such sort of apparatuses have been obtained : 1. Total amount of a large quantity of gas flow can be read from the volume scale of the gasmeter installed in such a by-pass. So far as discharge-coefficient of the gasmeter is constant, the voluminal ratio between these main and by-pass flow is constant over a wide range of main flow velocity, with negligibly small error. 2. The by-pass flow does not affect discharge-coefficient of the main flow nozzle. 3. An apparatus fitted for a given gas flow may be laid out with great accuracy. 4. The method may be applied satisfactorily to gas flow under any pressure either heigher or lower than the atmospheric pressure. As the method let no gas into atmosphere, it may be used even for poisonous or inflamable gas.

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By experiments, the author decided the mixing chamber length of the steam injector for boiler water feeding, which works at 0.5atg boiler pressure and 1.0atg delivery pressure. By shortening the mixing chamber length, the row steam parts (i.e. almost 8% of the steam consumption) flows through the diffuser throat at the low boiler pressure, and thus a delivery pressure higher than the boiler pressure can be obtained. By another experiments the author studied the mixing length limits of the steam injector for boiler water feeding.

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