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Your search keyword '"Groll, Eckhard A."' showing total 640 results
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640 results on '"Groll, Eckhard A."'

1. Field demonstration of predictive heating control for an all-electric house in a cold climate

Author

Pergantis, Elias N., Priyadarshan, Theeb, Nadah Al, Dhillon, Parveen, Ore, Jonathan P., Ziviani, Davide, Groll, Eckhard A., and Kircher, Kevin J.

Subjects
Electrical Engineering and Systems Science - Systems and Control
Abstract

Efficient electric heat pumps that replace fossil-fueled heating systems could significantly reduce greenhouse gas emissions. However, electric heat pumps can sharply increase electricity demand, causing high utility bills and stressing the power grid. Residential neighborhoods could see particularly high electricity demand during cold weather, when heat demand rises and heat pump efficiencies fall. This paper presents the development and field demonstration of a predictive control system for an air-to-air heat pump with backup electric resistance heat. The control system adjusts indoor temperature set-points based on weather forecasts, occupancy conditions, and data-driven models of the building and heating equipment. Field tests from January to March of 2023 in an occupied, all-electric, 208 m^2 detached single-family house in Indiana, USA, included outdoor temperatures as low as -15 C. On average over these tests, the control system reduced daily heating energy use by 19% (95% confidence interval: 13--24%), energy used for backup heat by 38%, and the frequency of using the highest stage (19 kW) of backup heat by 83%. Concurrent surveys of residents showed that the control system maintained satisfactory thermal comfort. The control system could reduce the house's total annual heating costs by about $300 (95% confidence interval: 23--34%). These real-world results could strengthen the case for deploying predictive home heating control, bringing the technology one step closer to reducing emissions, utility bills, and power grid impacts at scale.

Published
2024

9. Fuzzy modeling approach for transient vapor compression and expansion cycle simulation

Author

Kim, Donghun, Ma, Jiacheng, Braun, James E, and Groll, Eckhard A

Subjects
Moving boundary, Switching algorithm, Transient heat exchanger simulation, Fuzzy modeling, Engineering, Mechanical Engineering & Transports
Abstract

Previous mode switching algorithms for heat exchanger moving boundary models in the literature are composed of a set of IF-THEN rules. These representations could lead to numerical challenges due to the inherited discontinuities associated with IF-THEN rules. This paper presents an alternative mode switching methodology which results in a continuous moving boundary heat exchanger model over all possible mode changes. Numerical performance of the proposed method for a heat exchanger has been tested using simulations and sample results are compared with a moving boundary model with switching based on IF-THEN rules and also a finite-volume method. The proposed switching algorithm was implemented within a complete vapor compression cycle model and results were compared with experimental data for a start-up transient.

Published
2021

37. Analytical prediction of stress and strain in adhesive tube-to-tube joints under thermal expansion/contraction.

Author

Liu, Haotian, Weibel, Justin A., and Groll, Eckhard A.

Subjects
ADHESIVE joints, THERMAL expansion, STRESS concentration, DEAD loads (Mechanics), THERMAL strain, THERMAL stresses
Abstract

Adhesive joints are widely applied and studied for various industrial applications. The interest in adhesive joints has expanded to include heating, ventilation, air conditioning, and refrigeration (HVAC&R) systems having a significant number of joints employed for manufacturing. This study investigates an analytical modeling approach for predicting joint stress and strain distribution under static loading with thermal strain. A review of modeling techniques identified the need to develop a joint analytical model under loading conditions representative of HVAC&R applications. The details of the model, governing equations, assumptions, boundary conditions, and solution techniques are first reported. The model is validated via comparison to existing results before performing parametric studies to provide insights on the influences of thermal expansion and inner tube pressure on possible failure. It is found that the joint overlap length plays an important role in stress distribution, while the adhesive thickness has less impact. Overall, the results indicate that static loading failure is not likely a concern for joints in HVAC&R systems, but the thermal strain and stress induced by temperature fluctuations must be carefully considered. This modeling effort establishes a framework that can be used to generate criteria and instructions on designing adhesive joints across different HVAC&R [ABSTRACT FROM AUTHOR]

Published
2023
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