Water Source Heat Pump for Modular Classrooms

摘要

This work investigates and recommends design improvements for a water source heat pump system for mobile homes and modular classrooms. It builds on a previous study that tested a 3-ton geothermal heat pump in a modular classroom at Wilson Mills Elementary School in Johnston County, North Carolina. Water stored in flexible plastic bladders resting on the ground underneath the classroom served as the heat source. The bladders were filled with 2,000 gallons of saltwater. Using TRNSYS, a model of the original system was constructed and validated by comparing model predictions to measured performance. TRNSYS models of several new designs were constructed to evaluate potential design improvements. The system models were evaluated based on predicted performance for a typical meteorological year, and on other criteria such as initial cost, maintenance, and portability. This resulted in a new optimized system design in which the water storage volume is reduced to 120 gallons, and the predicted electrical energy requirements are about two-thirds of those of an air source heat pump. The predominant design improvement is to replace the bladders with heat exchangers constructed of PVC pipe. Design, costs, and assembly procedures for the PVC heat exchanger are presented in this article.