ABSTRACTThe rate of heat transfer is required in designing and sizing the heat transfer surface necessary for heat exchangers. A heat transfer correlation equation was determined for a rotary steam‐coil vacuum evaporator for concentrating tomato juice at the temperature difference of 120–130°F. A Nusselt‐type dimensionless equation was obtained as follows: hoDt/k = 0.60 XS‐2.5 1(ρND2c/μ)0.6 2(cpμ/k)1/3μ/μW)0,14in which hois the film coefficient for the product side of coil surface; Dcis the ouside diameter of rotary coil; Dtis the inside diameter of the mixing vessel; k is the thermal conductivity; XSis the solids content in decimal; ρ is the density; N is the speed of the rotary coil; μ is the viscosity; and cpis the specific heat. All fluid properties were evaluated at the arithmetic mean temperature of the bulk fluid and the wall except the μW which was evaluated at the wall temperature. The Reynolds number is in the range of 1–200 and sol
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