title: Optimal waste stream discharge temperature selection for dryer operations using thermo-economic assessment

authors: Walmsley, Timothy Gordon

subjects: heat recovery

abstract: A typical drying process that has liquid and gas discharge streams has been analysed and the impact of selecting various combinations of soft temperatures on heat recovery, utility targets, area targets, capital cost and total cost is reported. The method is based on the plus-minus principle and traditional pinch analysis methods for utility, area and capital cost targeting with the modification of using a ΔT contribution. Results show that there is significant benefit from optimising discharge temperatures for total cost. To achieve minimum energy consumption and total cost, heat recovery from the dryer exhaust air is necessary. Heat recovery from liquid heat sources is shown to be preferable over gas streams due to a higher film coefficient resulting in less heat exchanger area and capital cost. There is also value in making process modifications, such as combining streams or removing small streams to be solely heated by utility, to reduce the number of network heat exchangers. For the best case, the discharge temperatures of the leaving streams are 18.0 °C for water condensate (liquid stream) and 52.4 °C for the exhaust air (gas stream).

text: Optimal waste stream discharge temperature selection for dryer operations using thermo-economic assessment A typical drying process that has liquid and gas discharge streams has been analysed and the impact of selecting various combinations of soft temperatures on heat recovery, utility targets, area targets, capital cost and total cost is reported. The method is based on the plus-minus principle and traditional pinch analysis methods for utility, area and capital cost targeting with the modification of using a ΔT contribution. Results show that there is significant benefit from optimising discharge temperatures for total cost. To achieve minimum energy consumption and total cost, heat recovery from the dryer exhaust air is necessary. Heat recovery from liquid heat sources is shown to be preferable over gas streams due to a higher film coefficient resulting in less heat exchanger area and capital cost. There is also value in making process modifications, such as combining streams or removing small streams to be solely heated by utility, to reduce the number of network heat exchangers. For the best case, the discharge temperatures of the leaving streams are 18.0 °C for water condensate (liquid stream) and 52.4 °C for the exhaust air (gas stream).

year: 2012

title: Suppression of natural convection heat transfer coefficients in an attic shaped enclosure

authors: Anderson, Timothy Nicholas

subjects: triangular enclosure

abstract: The use of convection suppression devices has been widely discussed in the literature as a means of reducing natural convection heat loss from enclosed spaces. In this study the use of a single baffle was examined as a possible low cost means of suppressing heat loss by natural convection in an attic shaped enclosure.
Recently the authors experimentally demonstrated that the natural convection heat transfer for an attic shaped enclosure with Grashof Numbers in the range of 107 to 109 [1] could be predicted using a correlation in the literature developed for Grashof Numbers in the range 10⁵ and 10⁶ [2]. However, in this study the impact of adding a single baffle to the enclosure was examined. It was found that the heat transfer coefficient changes with increasing baffle length, and can be predicted using a modified form of the correlation presented in [1], as shown in Eq. Nu = 0.286A⁻⁰˙²⁸⁶Gr⁰˙²⁵(1-L/H) ⁰˙²

text: Suppression of natural convection heat transfer coefficients in an attic shaped enclosure The use of convection suppression devices has been widely discussed in the literature as a means of reducing natural convection heat loss from enclosed spaces. In this study the use of a single baffle was examined as a possible low cost means of suppressing heat loss by natural convection in an attic shaped enclosure.
Recently the authors experimentally demonstrated that the natural convection heat transfer for an attic shaped enclosure with Grashof Numbers in the range of 107 to 109 [1] could be predicted using a correlation in the literature developed for Grashof Numbers in the range 10⁵ and 10⁶ [2]. However, in this study the impact of adding a single baffle to the enclosure was examined. It was found that the heat transfer coefficient changes with increasing baffle length, and can be predicted using a modified form of the correlation presented in [1], as shown in Eq. Nu = 0.286A⁻⁰˙²⁸⁶Gr⁰˙²⁵(1-L/H) ⁰˙²

year: 2010

title: The use of Māori words in National Science Challenge online discourse

authors: Calude, Andreea S.

abstract: This paper presents data relating to the use of Maori borrowings as they occur in a corpus of scientific discourse on the websites of the eleven National Science Challenges (NSCs) and their associated Twitter feeds.

text: The use of Māori words in National Science Challenge online discourse This paper presents data relating to the use of Maori borrowings as they occur in a corpus of scientific discourse on the websites of the eleven National Science Challenges (NSCs) and their associated Twitter feeds.

year: 2018