Combination direct and indirect closed circuit evaporative heat

Abstract

A heat exchange apparatus which can be used as an evaporative condenser, fluid cooler or wet-air cooler, is provided with a direct evaporative heat exchange section overlying an indirect evaporative heat exchange section. An air entry zone common to both heat exchange sections receives an air stream blown into this zone by at least one fan, thereby pressurizing the plenum such that the air stream is forced to split and enter each section while inside the apparatus. This eliminates the need for separate air entries, thus condensing the size and cost of the apparatus, while increasing heat exchange capacity. A countercurrent air flow pattern through the direct section provides a uniformly cooled evaporative liquid for use in the indirect section. The evaporative liquid flow is parallel to the air stream provided in the indirect section. A process fluid inside the circuits of the indirect section can accept or reject heat from the evaporative liquid received from the direct section, with a part of the heat being is transferred into the indirect section air stream in sensible and latent form, thus increasing or decreasing the enthalpy of the air stream. The remaining heat can be either stored or released from the evaporative liquid to increase or decrease its temperature. The evaporative liquid is collected in a sump and then pumped upwardly for re-distribution across the direct evaporative heat exchange section.