title: Integration of solar heating into heat recovery loops using constant and variable temperature storage

authors: Walmsley, Michael R.W.

subjects: SELECTION

abstract: Solar is a renewable energy that can be used to provide process heat to industrial sites. Solar is extremely variable and to use it reliably thermal storage is necessary. Heat recovery loops (HRL) are an indirect method for transferring heat from one process to another using an intermediate fluid (e.g. water, oil). With HRL’s thermal storage is also necessary to effectively meet the stop/start time dependent nature of the multiple source and sink streams. Combining solar heating with HRL’s makes sense as a means of reducing costs by sharing common storage infrastructure and pipe transport systems and by lowering nonrenewable hot utility demand. To maximise the value of solar in a HRL, the means of controlling the HRL needs to be considered. In this paper, the HRL example and design method of Walmsley et al. (2013) is employed to demonstrate the potential benefits of applying solar heating using the HRL variable temperature storage (VTS) approach and the conventional HRL constant temperature storage (CTS) approach. Results show the VTS approach is superior to the CTS approach for both the non-solar and solar integration cases. When the pinch is around the hot storage temperature the CST approach is constrained and the addition of solar heating to the HRL decreases hot utility at the expenses of increased cold utility. For the VTS approach the hot storage pinch shifts to a cold storage pinch and increased heat recovery is possible for the same exchanger area without solar. With solar the VTS approach can maintain the same heat recovery while also reducing hot utility still further due to the presence of solar, but only with additional area. When the pinch is located around the cold storage temperature, solar heating can be treated as an additional heat source and the benefits of CTS and VTS are comparable.

text: Integration of solar heating into heat recovery loops using constant and variable temperature storage Solar is a renewable energy that can be used to provide process heat to industrial sites. Solar is extremely variable and to use it reliably thermal storage is necessary. Heat recovery loops (HRL) are an indirect method for transferring heat from one process to another using an intermediate fluid (e.g. water, oil). With HRL’s thermal storage is also necessary to effectively meet the stop/start time dependent nature of the multiple source and sink streams. Combining solar heating with HRL’s makes sense as a means of reducing costs by sharing common storage infrastructure and pipe transport systems and by lowering nonrenewable hot utility demand. To maximise the value of solar in a HRL, the means of controlling the HRL needs to be considered. In this paper, the HRL example and design method of Walmsley et al. (2013) is employed to demonstrate the potential benefits of applying solar heating using the HRL variable temperature storage (VTS) approach and the conventional HRL constant temperature storage (CTS) approach. Results show the VTS approach is superior to the CTS approach for both the non-solar and solar integration cases. When the pinch is around the hot storage temperature the CST approach is constrained and the addition of solar heating to the HRL decreases hot utility at the expenses of increased cold utility. For the VTS approach the hot storage pinch shifts to a cold storage pinch and increased heat recovery is possible for the same exchanger area without solar. With solar the VTS approach can maintain the same heat recovery while also reducing hot utility still further due to the presence of solar, but only with additional area. When the pinch is located around the cold storage temperature, solar heating can be treated as an additional heat source and the benefits of CTS and VTS are comparable.

year: 2013-01-01

title: Critical sets of 2-balanced Latin rectangles

authors: Cavenagh, Nicholas J.

subjects: Mathematics

abstract: An (m, n, 2)-balanced Latin rectangle is an (Formula presented.) array on symbols 0 and 1 such that each symbol occurs n times in each row and m times in each column, with each cell containing either two 0’s, two 1’s or both 0 and 1. We completely determine the structure of all critical sets of the full (m, n, 2)-balanced Latin rectangle (which contains 0 and 1 in each cell). If m, (Formula presented.), the minimum size for such a structure is shown to be (Formula presented.). Such critical sets in turn determine defining sets for (0, 1)-matrices.

text: Critical sets of 2-balanced Latin rectangles An (m, n, 2)-balanced Latin rectangle is an (Formula presented.) array on symbols 0 and 1 such that each symbol occurs n times in each row and m times in each column, with each cell containing either two 0’s, two 1’s or both 0 and 1. We completely determine the structure of all critical sets of the full (m, n, 2)-balanced Latin rectangle (which contains 0 and 1 in each cell). If m, (Formula presented.), the minimum size for such a structure is shown to be (Formula presented.). Such critical sets in turn determine defining sets for (0, 1)-matrices.

year: 2016

title: Foreword- Rotorua Lakes Symposium 2013

authors: Green, John

abstract: The Rotorua Te Arawa Lakes programme is now at a critical phase where nutrient budgets are to be established for landowners across the catchment of Lake Rotorua. The challenge is to reduce the existing nutrient load to the lake by over 43% by 2032.

text: Foreword- Rotorua Lakes Symposium 2013 The Rotorua Te Arawa Lakes programme is now at a critical phase where nutrient budgets are to be established for landowners across the catchment of Lake Rotorua. The challenge is to reduce the existing nutrient load to the lake by over 43% by 2032.

year: 2013