On the power law and quadratic forms for representing the leakage-pressure relationship- Case studies of sheltered chambers

Zheng, Xiaofeng; Wood, Christopher

Abstract

The leakage characteristics of a building can be described by a leakage-pressure relationship, which sometimes is referred to as flow-pressure relationship. This relationship provides the leakage rate through the building envelope when it is subject to a certain pressure difference across it and this can be represented by a mathematical equation. The most widely used form is a power law equation, which gives a good empirical description of this relationship. However, an alternative in the form of a quadratic equation is preferred by some researchers for various reasons. The pros and cons of both equations have been compared and discussed for a number of years. The argument usually lies in the accuracy of the equations in representing the flow at low pressures. This paper aims to interpret the theoretical understanding of the envelope flow from the fluid mechanics’ perspective and provide some insight as to how both equations perform when predicting the leakage flow at low pressures using test data obtained in sheltered environments. The accuracy of the predicted leakages at low pressures is then assessed by comparing them with directly measured values. It was found that both equations provide good curve fitting to the measurements. However, the power law equation gave slightly more accurate predictions (by up to 6%) on the leakage at low pressures than the quadratic equation in most scenarios in this study.

Citation

Zheng, X., & Wood, C. (2020). On the power law and quadratic forms for representing the leakage-pressure relationship- Case studies of sheltered chambers. Energy and Buildings, 226, Article 110380. https://doi.org/10.1016/j.enbuild.2020.110380

• Journal Article Type: Article
• Acceptance Date: Aug 7, 2020
• Online Publication Date: Aug 10, 2020
• Publication Date: Nov 1, 2020
• Deposit Date: Aug 7, 2020
• Publicly Available Date: Aug 11, 2021
• Journal: Energy and Buildings
• Print ISSN: 0378-7788
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 226
• Article Number: 110380
• DOI: https://doi.org/10.1016/j.enbuild.2020.110380
• Keywords: Building airtightness; Power law; Quadratic; Mathematical representation; Leakage-pressure relationship
• Public URL: https://nottingham-repository.worktribe.com/output/4815599
• Publisher URL: https://www.sciencedirect.com/science/article/abs/pii/S0378778820314316