Textile-based heat exchanger for humidity recovery between spatially separated air flows

Abstract

Both, sensible heat recovery and the combined heat and humidity recovery are state of the art. Of particular importance is humidity recovery in winter season. The transfer of water vapour from the humidity-laden extract air to the very dry outdoor air is very important for a good room air quality. Enthalpy exchangers potentially reduce the energy requirements of any subsequent air humidification on the supply air side considerably. In the planning phase, the possibility of enthalpy recovery is therefore often used as a weighty argument for dispensing with humidification systems. However, all systems established on the market require a coupling of supply air and extract air by means of recuperation (e.g. plate heat exchanger) or direct regeneration (rotating storage mass). Nevertheless, enthalpy recovery systems for HVAC-Systems with spatially separated supply air and extract air are not available on the market. In order to close this gap in the market, ILK Dresden has developed textile-based heat exchangers, which - integrated in closed loop systems - can transfer humidity as well as sensitive heat between spatially separated air flows (e.g. between supply air and exhaust air). The functional principle is based on a liquid sorption process via semipermeable membranes. This is regardless of whether it is a 2-fluid system (air, brine), in which the heat-transferring fluid and the mass-transferring fluid is the same fluid and only one circuit is utilised, or a 3-fluid system (air, brine, water), in which the fluids involved flow in separated circuits. In general, the developed system can be used all year round - thus also for air dehumidification or indirect evaporative cooling processes. The current state of development is presented. In addition, an outlook is given for which applications the textile heat exchangers could be further developed and which application potentials are offered.