Experimental Investigation on Natural Convective Heating of Milk

Abstract

In this article, the behavior of heat and mass transfer relation during khoa making has been investigated. Various indoor experiments have been performed for simulation of developed thermal model for maximum evaporation during heating of milk. The data obtained from experimentation have been used to determine values of constant “C” and exponent “n” by simple regression analysis. Based on the values of “C” and “n,” convective and evaporative heat transfer coefficients for milk were determined. It was observed that the convective and evaporative heat transfer coefficients decrease with the increase in rate of heating (varying voltage). It was also observed that convective and evaporative heat transfer coefficients increase with the increase in operating temperature. The rate of increment of evaporative heat transfer coefficient is higher than the convective heat transfer coefficient. The experimental error in terms of percent uncertainty was also calculated. PRACTICAL APPLICATIONS The traditional method of khoa making (i.e., open pan evaporation process) requires a large quantity of energy and in the present era, energy saving is needed to pay sufficient attention. In rural India, generally, wood, cattle dung, coal, kerosene, etc. are used in open chulah as fuel for khoa making which is hardly 8–10% thermally efficient. A number of research articles are available in the literature explaining the mechanization of khoa making process. But even today, the khoa making technology in rural India much remains the same. Thus, by keeping energy saving aspect in mind, the traditional method of khoa making has been further explored.

Evaporative Heat Transfer Coefficients During Sensible Heating of Milk

“…The evaporative heat transfer coefficients were observed to decrease 129.23% for the given range of heat inputs. The evaporative heat transfer coefficients obtained for sensible heating of milk in a stainless steel pot were compared with the values reported by Kumar et al, [12] for sensible heating of milk in an aluminum pot (Figure 2). It can be seen that the evaporative heat transfer coefficients during sensible heating of milk in a stainless steel pot follows the same trend as reported for the case of an aluminum pot.…”

“…The heating of milk during khoa making involves sensible heating and boiling convection heat transfer phases. Recently, Kumar et al., [12,13] experimentally evaluated the convective heat transfer coefficients during sensible heating of milk in aluminum [12] and stainless steel pots [13] [12,13]. The present research work may be helpful in designing an evaporator for khoa production.…”

“…The evaporative heat transfer coefficient (h e ) was calculated from Equation (1) which is given as [12,14]: The data obtained from experimentation were used to determine the values of the convective heat transfer coefficients. The details of the convective heat transfer coefficient values used for determining the evaporative heat transfer coefficients are given elsewhere [13].…”

“…The different physical properties of humid air, such as specific heat (C v ), thermal conductivity (K v ), density (ρ v ), viscosity (μ v ), and and partial vapor pressure, P(T) were determined by using following expressions [12,13] …”

Forced Convection Drying of Indian Groundnut: An Experimental Study

“…(8) are obtained by using simple linear regression formulae. The EHTC, h e , is evaluated as [35] ( ) ( ) 0.016…”