Nuclear Engineering and Design 241 (2011) 2006–2012 Contents lists available at ScienceDirect Nuclear Engineering and Design journal homepage: www.elsevier.com/locate/nucengdes Turbulent cooling water discharge into still body of water Jafar Ali ∗ , John Fieldhouse, Chris Talbot University of Huddersfield, Queensgate, Huddersfield, HD1 3DH, United Kingdom article info Article history: Received 2 May 2010 Received in revised form 8 August 2010 Accepted 10 August 2010 abstract This paper is concerned with the development of a predictive tool to determine the heat diffusion profile for turbulent discharge of heated water into a body of still receiving water. The process makes use of a thermal imaging camera to measure the discharge plume from a range of sites in order to observe the actual discharge and then to provide a mathematical model that will allow British Waterways to satisfy the Environmental Agency regulations. In addition the sites are replicated in a laboratory environment with a scale model tank that allows the mixing zones to be measured under variable conditions. In this case the heated water is dyed to provide a visual plume in addition to the thermal image. The plume and mixing zones are then predicted using appropriate software such as Matlab, the model being optimised to reflect the real measured discharges. © 2010 Elsevier B.V. All rights reserved. 1. Introduction The concerns of global warming are guiding most industries towards addressing their energy usage. In large buildings, where air conditioning is required, there is generally a need for “chillers” to control the temperature of the building. This process is not environmentally friendly and expensive in terms of energy used and maintenance issues. The alternative is to cool using natural resources such as rivers and canals but historically this has not been used to maximum effect because of the inappropriate predic- tion “tools” used to evaluate how much energy could be “dumped” into a given site. Earlier models were one-dimensional and were extremely conservative in their analysis so rejecting many pro- posals. This research is aimed at addressing that situation and to provide a valuable interactive three-dimensional predictive tool that will better evaluate the potential of using any canal site for cooling purposes. Water is normally withdrawn from natural or artificial sources to the cooling system heat exchanger. The water increases in tem- perature as it cools the system and is then discharged back into the lakes, rivers or canals resulting in a rise in the bulk temperature of the surrounding water. The main effect of the increase in ambient water temperature is the reduction of the dissolved oxygen which might put fish life and other aquatic life-form at risk. The increase in temperature also has an affect on the balance of the natural and biological processes in the water. There are large numbers of stud- ies of this type regarding water mixing, i.e., heated water discharge into cooler water. The majority of them are based on assumptions, ∗ Corresponding author. E-mail addresses: j.ali@hud.ac.uk (J. Ali), j.d.fieldhouse@hud.ac.uk (J. Fieldhouse). some use experimental model tanks but do not validate with real field trials whereas others only make use of mathematical mod- els and again do not validate with field trials. This paper provides a holistic approach to the study of heated water discharged into still water. It makes use of a thermal camera to observe the dis- charge plume and map the plume profile on the surface of the water. In addition the study uses a laboratory scale model tank to replicate a diversity of conditions and allows the thermal images to be validated using dyed and heated discharge water. On-site test- ing and data collection over a three dimensional grid completes the empirical work for subsequent use in validating an effective and interactive mathematical model. This uses Matlab software to provide a three dimensional distribution of heat dissipation within the receiving water. In addition the earlier approaches regarded the diffusion coefficient as constant whereas this work uses differ- ing values of diffusivity with the turbulent diffusivity and thermal molecular diffusion coefficients being applied to each grid point in the mixing zone. This approach yields a different shape for the plume/mixing zone, in which the boundary of the plume is more representative of the observed results. Although this work is cur- rently limited to the study of heated water discharge into the body of stagnant (still) receiving water it is adaptable in future to account for moving water. The majority of work in this paper concentrates on the initial process – that of determining the heat diffusion pro- file and plume shape on the surface of the receiving water. At the moment the University of Huddersfield have three sites licensed to extract water for cooling purposes. All these sites have compre- hensive records and all show that the process is safe for aquatic life. British Waterways’ one dimensional mathematical model sug- gests they will not be safe and if the model is over-conservative in its prediction then British Waterways may be rejecting licensing applications that are in reality safe. It is this situation that demands 0029-5493/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.nucengdes.2010.09.005