Development and application of test cases for comparing vertical ground heat exchanger models

The main objective of this paper is to establish a set of test cases for analytical verifications and intermodel comparisons of ground heat exchanger (GHX) models used in building simulation programs. Several test cases are suggested. They range from steady-state heat rejection in a single borehole to varying hourly loads with large yearly thermal imbalance in multiple borehole configurations. The usefulness of the proposed test cases is illustrated by running them with different GHX models. This comparison exercise has shown that 1-D models compare favourably well with the more elaborate 3-D models for relatively small simulation periods. The cyclic heat rejection/collection test has revealed some small deficiency in the load aggregation scheme of a particular model. Finally, the use of the asymmetric (cooling-dominated) load profile test case for a bore field composed of 100 boreholes revealed that the borehole wall temperature predicted by two GHX models can differ by as much as 10oC after a 30 year simulation

An Integrated Solution for Commercial AC Chillers Using Variable Speed Scroll Compressors

For a couple of years already, variable speed compressor technology has become a standard for residential heating and cooling applications. Indeed, as a response to increasing performance requirements, small capacity variable speed scroll compressors optimized for heating and cooling applications were released and progressively adopted on the market. In January 2018, the first tier of the Ecodesign Directive (2009/125/EC) requirements defined for commercial AC chillers will enter into force across European Union. The application of this new regulation will most likely drive the European commercial AC market toward a similar direction than the residential market and a more intensive adoption of the variable speed technology, especially for systems below 400kW rating cooling capacity. This paper presents integrated solutions targeting efficient implementation of variable speed technology in commercial water chillers, allowing system manufacturers to face new regulatory challenges. The considered solution integrates multiple configurations of variable speed and fixed speed scroll compressors, variable frequency drive, electronic expansion valve and control. Compressors envelopes management and protection as well as superheat control capabilities are presented. Seasonal performance simulations have been realized according to EN14825 to quantify the gain of variable speed technology. Laboratory testing has been performed to develop and qualify the considered solution. Testing on a real Air-to-Water chiller has also been realized to fine-tune the control and measure the achieved efficiency levels

Development Of An Integrated Solution For Multi Scroll Compressors With Wet Vapor Injection

Extensive use of Heat Pumps is essential to meet European 20-20-20. Reversible air-to-water heat pump systems have to operate at high efficiency levels on a wide operating range to be an economical alternative to the traditional heating and cooling systems. This paper presents the advantages, the control and the implementation of multi vapor injected scroll compressors systems in commercial heat pump water heater application. Enhanced Vapor Injection (EVI) technology allows both performance and reliability improvement across the compressors operating area, especially at low ambient temperatures. Wet Vapor Injection allows extending compressors operating range at very low ambient and high condensing temperatures. The development of a solution integrating injection capable scroll compressors, expansion valves and wet/vapor injection control system is presented in this paper

An Integrated Solution Enabling Low Superheat Operation for Improved Performance in Reversible Chiller Systems

The adoption and proliferation of variable speed compressors and electronic expansion valves (EXVs) in high-efficiency reversible chiller systems provides the opportunity to optimize the performance of the unit around a new set of variables. This paper details the benefits of a controls framework designed to enable low-superheat (below 5K) operation to optimize the seasonal energy efficiency ratio (SEER) of a commercial-scale chiller in a safe manner. The various attributes of low-superheat operation over conventional (\u3e5K) chiller operation, including the reliability impact on the controller and compressor, is discussed. The performance benefit for a range of capacities and compressor configurations, with particular attention to evaporator effectiveness, is also presented. In addition, the results of the associated reliability campaign to guarantee the integrity of the system for continuous low-superheat operation is detailed. Ultimately, this provides a template from which significantly improved system performance can be achieved