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SUMMARYAn investigation has been made into the effect of oil concentration on evaporation heat transfer coefficients in refrigerant-oil mixtures flowing in a horizontal tube. A new correlation is presented for heat transfer coefficients in convective evaporation of refrigerant-oil mixtures that predicts the results of the present study within approximately f 20%. The paper reports measurements of evaporation heat transfer coefficients in refrigerants R12 and R22, both oil-free and with two concentrations of Shell Clavus 32 oil. A 1.8 m long 2 in O/D copper tube (8.05 mm I/D) was used, at evaporation temperatures of -5"C, 0°C and + 5°C. Heat flux and mixture mass velocity were kept constant at 2500 W m-2 and 155 kg m-' s -l , respectively, and measured coefficients were in the range of 1400 to 3900 W m-* K-I. The results showed that, for a complete evaporator, 2% oil may be expected to increase the heat transfer coefficient by 12%, but 10% oil returns the coefficient to oil-free values.

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The missing‐data‐residue technique is a method of recovering the scatter intensity curve at low‐Q values from small‐angle scattering data. The effect on the missing‐data‐residue technique of the addition of varying degrees of noise to truncated analytical particles is investigated, with the noise levels varying from 0 to ±10%. The effects of smoothing of the data prior to the application of the technique are also investigated. The results for nonsmoothed data are shown to degrade in proportion to the noise level and it is shown that an estimate of the noise level gives an estimate of the potential error on the result. The five‐point moving‐average smoothing used is shown to improve the variance of the returned zero‐angle scatter intensity but at the expense of potentially introducing a small error. Results for both smoothed and nonsmoothed data are compared and it is shown that smoothing of the data is preferable, even at relatively low noise levels. For both smoothed and nonsmoothed data, a correlation is shown to exist between the error on the first known I(Q) data point and the returned I(0).

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