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Component Evaluation of a Novel Integrated Liquid Desiccant Air Conditioning System (IDCS)

Introduction

This chapter presents component evaluation, based on experimental data, of a novel ‘integrated’ liquid desiccant air conditioning system (IDCS) operating with a potassium formate solution. It evaluates the novel system under a variety of environmental and operating conditions in a controlled laboratory environment, with the aim of facilitating effective tri-generation system integration in Chap. 7.

As previously discussed in Chap. 2, there are some clear operational advantages to the use of liquid desiccant air conditioning systems over conventional VCS in building applications. The advantages are a low electrical requirement, the replacement of electrical energy with thermal energy (this can be waste or process heat) and high latent control. Liquid desiccant air conditioning also offers significant advantages over other thermally activated air conditioning technologies, particularly in a tri-generation system application. The advantages are a potential to use low grade waste heat at temperatures of less than 60 °C and operation at atmospheric pressure. Although extensive work has been carried out on liquid desiccant air conditioning systems (Halliday et al. 2002; Gommed and Grossman 2007; Beccali et al. 2012; Hassan and Mohamad 2012), to date system complexity has severely limited their wider application and outweighed the significant energy savings they can achieve (Jain and Bansal 2007). Furthermore, space, complexity and leakage are often cited as a significant barrier to the wider use of liquid desiccant air conditioning in building and tri-generation system applications (Jain and Bansal 2007). There is therefore a need for simpler, more compact systems, particularly for building and tri-generation system applications. Additionally, across all applications, issues of liquid desiccant entrainment in the supply airstream and the risk of HVAC equipment corrosion need to be addressed.

© Springer International Publishing AG 2017

T. Elmer, A Novel SOFC Tri-generation System for Building Applications, Springer Theses, DOI 10.1007/978-3-319-46966-9_5

A novel IDCS has been developed with the aim of addressing the highlighted issues, therefore permitting effective integration of liquid desiccant air conditioning technology in building and tri-generation system applications. The novel IDCS presented in this chapter has three design characteristics that aim to address the issues of size, leakage and corrosion:

  • (1) A novel stack design integrates the regenerator, evaporative inter-cooler and dehumidifier into a single heat and mass exchanger (HMX) core, making the whole system more compact and less prone to leakage. The IDCS has less piping, heat exchangers and pumps compared to an equivalent conventional ‘separate’ system.
  • (2) The use of a semi-permeable micro porous membrane in the dehumidifier and regenerator HMX cores to prevent desiccant entrainment into the supply airstream.
  • (3) Employment of an environmentally friendly, non-corrosive and low cost potassium formate (CHKO2) desiccant solution.

No previous work has been found in the literature regarding an integrated design combining the regenerator, evaporative inter-cooler and dehumidifier into a single HMX core, thus the work presented is a clear contribution to knowledge. The work presented in this chapter progresses the fields of liquid desiccant air conditioning technology for building and tri-generation system applications. The IDCS has been acquired from the company Intelligent Integration of Solar Air and Water (IISAW) in China, but has been tested at The University of Nottingham. Detailed component testing of the IDCS under controlled laboratory conditions generates greater understanding of the system and its performance, but more specifically it facilitates the following:

  • (1) Highlight the impact changes in environmental and operating conditions have on the performance of the dehumidifier, regenerator and complete IDCS.
  • (2) Recording of the operating conditions in which the dehumidifier and regenerator processes are balanced i.e. the mass of water absorbed in the dehumidifier is equal to the mass removed in the regenerator. This will allow continuous operation of the IDCS across a range of working requirements.
  • (3) Discuss the potential for tri-generation system integration. Selection of optimised operating conditions for the IDCS, with particular consideration to trigeneration system integration i.e. hot water flow rate and temperature from the SOFC CHP system.

The chapter is presented in three sections. Section 5.2 describes the IDCS experimental set-up, instrumentation and experimental method. Section 5.3 presents the IDCS experimental results and analysis. Section 5.4 concludes the chapter and discusses the potential for tri-generation system integration. A published journal article, by the author, on the novel integrated liquid desiccant air conditioning system can be referred to here; Elmer et al. (2016c).

 
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