Heat transfer analysis and effects of feeding tubes arrangement, falling film behavior and backsplash on ice formation around horizontal tubes bundles Hani Hussain Sait King Abdulaziz University, Rabigh, PO Box 344, Rabigh 21911, Saudi Arabia article info Article history: Received 23 November 2011 Accepted 2 May 2013 Available online 5 June 2013 Keywords: Freezing Falling film Ice storage abstract Excessive electrical load has recently get a lot of attention from electric companies specially in hot coun- tries like Saudi Arabia, where air-conditioning load represents about 75% from the total electrical load. Energy storage by freezing is one of the methods that used to tackle this issue. Ice is formed around hor- izontal cold tubes that are subjected to falling film of water. Ice quantity is measured, photographed and studied. In this studied the coolant inside the tubes flows in series tube arrangement. The results are compared with previous study in which parallel arrangement was used. In addition the falling film behavior and the resulted backsplash are also investigated. A mathematical model to predict ice forma- tion around the tube is proposed. Comparison of the results of the model with that of the experiments showed that the agreement between the two is acceptable. The results also show a quite reasonable quantity of ice is formed in a short time and the series arrangement is more efficient than parallel one. The falling film shapes and its backsplash has also affected the ice formation. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction Electric companies face a problem of excess loading during sum- mer time at the peak loading period, which usually take place in the afternoon time between 12 and 5 pm. During this time most of the electric load goes mainly to air-conditioning, in which people stays at home and others still at work. Plus it is an official work time for companies and factories. Load management initiatives are usually investigated by the electric companies to smooth the system load curve (Fig. 1) and, in this way, avoid the installation of extra equip- ment to handle the excessive load. Many methods are suggested to handle this problem. Different financial Tariff for the KW prices is used in some countries. Electric companies often structure rates to encourage customers to minimize demand during peak periods. Other is the use of electrical link between some countries that has different working times or different weathers. Fahlen et al. [1] has discussed the integration of heat-driven absorption cooling (AC) technology in a district heating and cooling (DHC) system which raises the district heat (DH) demand during low-demand periods and may thus contribute to more efficient resource utilization. The case study has been done in Sweden where the cooling demand is rapidly increasing. The study was aimed to assess the potential for cost and CO 2 emission reduction due to expansion of DH-driven AC instead of electricity-driven compression cooling characterized by a high share of low-cost excess heat sources. The results showed that an increased cooling demand may be met by generation asso- ciated with low or even negative net CO 2 . Also, Caliskan et al. [2] have used energetic, exergetic, environmental and sustainability analyses for latent, thermo-chemical and sensible thermal energy storage (TES) systems for phase change material (PCM). These are expected to support the building applications under varying envi- ronment (surrounding) temperatures. According to the energy effi- ciency aspects of TESs, the discharging processes of the latent TES and the hot well of the aquifer TES possess the minimum and max- imum values of 5.782% and 94.118% at 8 °C dead state temperature, respectively. Also, the fan used with the latent TES is the most envi- ronmentally-benign system component among the devices. Unique solution that can save energy and will not cost so much is the storing of energy. Thermal energy can be stored as a chilled water or ice during the off peak load and then can be used during the peak load instead of operating cooling devices such as com- pressors. Chilled water storage tank is beneficial in use where water resources and space are available. Zinet et al. [3] have used a dynamic model for the simulation of a novel single-effect water/lithium bromide absorption chiller. Heat and mass transfer in the evaporator–absorber and in the desorber were described according to a physical model for vapor absorption based on Nus- selt’s film theory. The other heat exchangers were modeled using a simplified approach based on the NTU-effectiveness method. The simulations modeled the performance of the chiller as well repre- sented and consistent with expectations. Rivarolo et al. [4] has discussed on the thermo-economic optimum performance of 0196-8904/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.enconman.2013.05.010 E-mail address: hhsait@kau.edu.sa Energy Conversion and Management 73 (2013) 317–328 Contents lists available at SciVerse ScienceDirect Energy Conversion and Management journal homepage: www.elsevier.com/locate/enconman