Conceptual design and selection of HVAC&r systems by combining knowledge based expert system with a building energy simulation program

The typical HVAC&R design process generates several alternative solutions (configurations of systems, subsystems and components), and then utilizes analysis and estimation tools to select a ‘best’ solution based on predefined selection criteria such as lowest Life Cycle Cost (LCC). This approach is limited by the engineer's experience, capabilities and time constraints, often resulting in missed opportunities for optimum system selection. Further, the latest equipment, design approaches, and concepts are not even considered. Knowledge-Based Expert System (KBES) can augment the current advanced building simulation tools by creating one entity that automatically generates, analyzes, and sorts design solutions subject to both site and user constraints. This dissertation describes the design and proof-of-concept demonstration for a computer-based HVAC&R conceptual design assistant. The research focuses on methodologies to synthesize and analyze HVAC&R systems by employing KBES and building energy simulation programs such as DOE-2. A commercial hybrid KBES shell has been selected and then programmed to include HVAC&R knowledge of components and systems, resulting in an ability to synthesize design alternatives using rule-based and frame-based knowledge representation mechanisms. The KBES shell also includes procedural programming capabilities that have the ability to perform simple heuristic cooling and heating design loads as well as first and maintenance cost calculations. Initiation, configuration and matching rules have been incorporated into the KBES to begin generation of design alternatives, configure the secondary and primary subsystems, and match applicable secondary systems to primary systems through site, configuration, and subsystems matching constraints. The ASHRAE/IESNA 90.1-1999 standard has been used to set the minimum allowed energy performance for equipment including fans, chillers, boilers etc., resulting in compliance with energy codes. In order to demonstrate the efficacy of this approach, a knowledge base applicable to large office buildings has been developed. The newly developed KBES has been applied to two cases: (i) to demonstrate the process of HVAC&R systems synthesis and evaluation and (ii) to demonstrate the sensitivity of every initiation parameter. This research clearly demonstrates the feasibility and methodology of developing intelligent tools to assist the HVAC&R practitioner in the early stage of the design.