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Predicted percentage dissatisfied with vertical temperature gradient
Highlights 98 seated persons in a lab experiment with thermal stratification up to 8.4 °C/m. Temperature gradient has small impact on whole-body acceptability at 8.4 °C/m. We developed a model to estimate the predicted percentage dissatisfied (PPD∇T). Thermal sensation and vertical temperature gradient affect PPD∇T. 5 °C/m between head and feet is acceptable for whole-body thermal neutrality.
Abstract A vertical thermally stratified environment provides opportunities for improved ventilation effectiveness and energy efficiency, but vertical temperature gradient can also cause local thermal discomfort. ASHRAE 55 and ISO 7730 prescribe a 3 °C/m limit between head and feet for seated persons. However, an increasing amount of evidence suggests that this limit is too restrictive. To revisit how vertical temperature gradient affects local thermal comfort, we conducted laboratory tests with four nominal vertical temperature gradients (0.4, 2.9, 5.9, and 8.4 °C/m). Ninety-eight seated college-age students participated in a blind within-subject experiment. Cold-feet discomfort is more frequently rated than warm-head discomfort with increasing temperature gradients. By using logistic regression modeling, we show that the whole-body dissatisfaction increases only slightly (<10%) with vertical temperature gradient, even up to 8.4 °C/m. Sex does not significantly affect the results except at 8.4 °C/m. Acceptable vertical temperature gradient changes with thermal sensation votes. The results suggest that the vertical temperature gradient could be increased to 5 °C/m between head and feet when the subject is thermally neutral.
Graphical abstract Display Omitted
Predicted percentage dissatisfied with vertical temperature gradient
Highlights 98 seated persons in a lab experiment with thermal stratification up to 8.4 °C/m. Temperature gradient has small impact on whole-body acceptability at 8.4 °C/m. We developed a model to estimate the predicted percentage dissatisfied (PPD∇T). Thermal sensation and vertical temperature gradient affect PPD∇T. 5 °C/m between head and feet is acceptable for whole-body thermal neutrality.
Abstract A vertical thermally stratified environment provides opportunities for improved ventilation effectiveness and energy efficiency, but vertical temperature gradient can also cause local thermal discomfort. ASHRAE 55 and ISO 7730 prescribe a 3 °C/m limit between head and feet for seated persons. However, an increasing amount of evidence suggests that this limit is too restrictive. To revisit how vertical temperature gradient affects local thermal comfort, we conducted laboratory tests with four nominal vertical temperature gradients (0.4, 2.9, 5.9, and 8.4 °C/m). Ninety-eight seated college-age students participated in a blind within-subject experiment. Cold-feet discomfort is more frequently rated than warm-head discomfort with increasing temperature gradients. By using logistic regression modeling, we show that the whole-body dissatisfaction increases only slightly (<10%) with vertical temperature gradient, even up to 8.4 °C/m. Sex does not significantly affect the results except at 8.4 °C/m. Acceptable vertical temperature gradient changes with thermal sensation votes. The results suggest that the vertical temperature gradient could be increased to 5 °C/m between head and feet when the subject is thermally neutral.
Graphical abstract Display Omitted
Predicted percentage dissatisfied with vertical temperature gradient
Liu, Shichao (author) / Wang, Zhe (author) / Schiavon, Stefano (author) / He, Yingdong (author) / Luo, Maohui (author) / Zhang, Hui (author) / Arens, Edward (author)
Energy and Buildings ; 220
2020-04-22
Article (Journal)
Electronic Resource
English
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