An experimental investigation on the airside performance of fin-and-tube heat exchangers having corrugated louver fins - Part II; wet surface

Abstract

As slit area, m 2 At heat transfer area at the mid-plane of the tube wall, m 2 bf slope of the saturated air enthalpy curve at fin temperature, J/kgK br slope of the saturated air enthalpy curve between tube wall and water temperature, J/kgK bt slope of the saturated air enthalpy curve at tube wall temperature, J/kgK C heat capacity, W/K cp specific heat, J/kgK D tube diameter including fin collar thickness, m f friction factor h heat transfer coefficient, W/mK hs height of the slit, m i enthalpy, J/kg j Colburn j factor k thermal conductivity, W/mK Abstract In this study, two kinds of corrugated louver fin-and-tube heat exchangers – one having one corrugation per row and the other having two corrugations per row – were tested under wet condition, and the results were compared with those of the standard louver fin and the plain fin samples. The highest j and f factor were obtained for the double corrugated louver fin sample, followed by the single corrugated inclined louver fin sample, the standard louver fin sample and then the plain fin sample. This result is in contradiction with those obtained under dry condition, where the standard louver fin sample yielded the highest j and f factor. The high j and f factor of the corrugated louver fin sample may be due to the improved condensate drainage over the standard louver fin sample. Corrugated channels along with louvers of high louver angle of the corrugated louver fin samples appear to have resulted better condensate drainage. All the enhanced fin samples yielded larger heat transfer capacity than plain fin samples at the same pumping power. Furthermore, the largest heat transfer capacity per pumping power was obtained for the double corrugated louver fin sample, followed by the single corrugated louver fin sample and then the standard louver fin sample.