Heat transfer—a review of 1983 literature

Experiments were run to investigate the feasibility of a flash vaporization system for aircraft gas turbine engines. The experiments consisted of a determination of boiling points, dew points, critical temperature, critical pressure, heat transfer coefficients, deposit formation rates, and deposit removal in a flowing system. Three fuels were used in the experiments including Jet-A, Experimental Referee Broad Specification fuel (ERBS), and a premium No.2 diesel fuel. Engine conditions representing the Energy Efficient Engine (E3) at SLTO, cruise and idle were simulated in the vaporization system and it was found that single phase flow was mainrained in the heat exchanger and downstream of the throttle. Deposits encountered in the heat exchanger represented a thermal resistance as high as 1.3 x 10−3 M2K/watt and a deposit formation rate over 1000 μgC/cm2hr. It was found that the deposit can be removed by cleaning with air at a temperature of 720 K for 10 min.

Experimental Study of External Fuel Vaporization

A two-peak wall temperature profile was observed while flowing a kerosene-type gas turbine fuel through a direct-resistance heated tube at an entrance Reynolds number of about 1500. The downstream peak gradually diminished as deposits formed inside the tube, and only one peak remained after seven hours. The observation is explained qualitatively on the basis of analytical and experimental results reported in the literature. It is shown that the temperature profile can be divided into five regions: development of the thermal boundary layer, appearance of the secondary flows, fully developed thermal boundary layer, transition to turbulent flow, and turbulent flow. Deposits increase the tube roughness and reduce the length required for laminar-turbulent transition.

Tube entrance heat transfer with deposit formation

While flowing a kerosene-type gas turbine fuel through a direct-resistance heated tube, a condition was found which resulted in a tube wall temperature profile with two peaks near the tube entrance. The downstream peak gradually diminished as deposits formed inside the tube and only one peak remained after seven hours. On the basis of existing analytical studies and experimental data pertaining to heat transfer in the entrance region of tubes, it was concluded that the temperature profile can be divided into five regions: development of the thermal boundary layer, appearance of secondary flows, fully developed thermal boundary layer, transition to turbulent flow and turbulent flow. Deposits increased the tube roughness and reduced the length required for laminar-turbulent transition.

E. J. Szetela

Papers

Tube entrance heat transfer with deposit formation

Tube Entrance Heat Transfer with Deposit Formation