daniloronchi

I hope to be useful to post here this article I made. Feel free to ask and sorry if my technical english isn't perfect. You can find all the pictures and the spreadsheet here: http://www.danireef.com/2008/11/29/pompe-d...w/#returnpumps3 Albeit the language on the spreadsheet shown here is italian, the spreadsheet is provided in english too. Choosing the right return pump it’s never an easy task. The first problem is to understand the correct amount of water to be carried over in tank, and then finding a pump that could really brought that. I propose my idea on solving the first problem, and you can read at the bottom of this article. Here we are then to the second problem. Given the water amount we need, for example, 1,000 liters per hour, we must choose the correct pump. The first choice that seems logical is to buy a pump of 1,000 liters per hour or a little higher. This is wrong because this number is considerated at zero prevalence, in practice that shows us how much would carry the pump if it were used as pump movement, with no need of increasing share of water from the pump to a share higher. The difference of elevation gain by winning is just call prevalence. Each pump is accompanied by a chart that tells us how the scope to vary in prevalence. Simplifying the speech, and referring to the chart attached, if a pump is credited to a range from 2400 liters per hour and prevalence of 370 cm (data Eheim 1260), will mean that pump used as the movement will move to 2400 liters, and when connected to a pipe that will bring water to more than 370 cm, will fail to bring even one liter of water. The extent of a pump, however, varies not only with the prevalence, but also by other factors: for example curves acts as if they increased the prevalence, corrugated pipes, and so forth. The chart above shows the figures for the Eheim 1260. Scope of 2400 liters hour to 0 cm prevalence scope of anything the prevalence of 370 cm. The variation between the two units is considered linear. These values are difficult to calculate as you should use a non-linear equation, and probably not so important to the final result. I will act in this way (including what I wrote below for choosing the right return pump): 1. I consider the maximum amount of water that our skimmer can drive; 2. I increase this number by 10%; 3. I measure the difference between the share of output in water bath and the position of the pump, the prevalence; 4. I increase the prevalence of 15% to take into account all possible pressure drop, the wear of the tubes, curves and anything else; You get to have a pair of values of 1,000 +10% = 1.100 liters hour and 140cm + 15% = 161 cm prevalence to win. Now we have to choose our pump looking what market offers. In the excel file that I built are given the technical data of various pumps on the market to give an idea of the characteristics of each, their cost, and so that there is a simple spreadsheet that you can provide useful information for your choice. I have to make some distinctions on simplifications used in the spreadsheet. 1) Given the difficulty of finding the proper load curve of each pump, and in any case the difficulties of making mathematically the trend of a nonlinear curve, it was assumed valid as the linear relationship between size and prevalence, as if the curve was actually a line. 2) The calculation takes into account the prevalence alone, as this increased by 15% as suggested above, to calculate the actual, as a greater accuracy with the complication that take account of the curves, used materials etc there would have provided in any case a much more significant. Now for speaking purpouse we take into consideration the real case to see what happens really. To find the right flow we calculate the pressure drop, and we will consider the permanent motion under pressure, the equation is as follows: Permament motion of a fluid inside cylindrical pipeline is at least mildly uniform. The loss of total load per unit length of the pipe (H1-H2) / L = j is equal to the corresponding piezometrical drop (h2-h1) / L = i. It is obviously linked to the size characteristics of motion, and the conduct of fluid above the equator. Where * U = Q / Omega = average speed = flow / area of the section; * D = diameter of the pipe; * G = gravity acceleration = 9.81 m / sec ^ 2; * Lambda = dimensionless coefficient of friction (or resistance) function in general on the roughness of the pipe and the Reynolds number, which in turn depends on the density of the liquid, the dynamic viscosity and kinematic viscosity. The problem then does not end here, because we have to calculate all the pressure drops (periodic section, change of conduct, curves, etc) and then from all this seems clear that the exact mathematical treatment is not a simple matter, the equation also does not allow direct mathematical solution if not considering different tables, then we will study it in more easier way. To facilitate the task to all you can use the following spreadsheet, even to those who disagree with my logic of having a tank to sump flow bigger than flow of his skimmer. As we have said into the spreadsheet you can find the data pumps more used commercially for this task, at least in the Italian market, and where you can specify data if your pump is not covered. In the first line you have to report the only foundamental number, the prevalence. Possibly you can correct the percentage of correction that I place equal to 15% as specified in the text, in this way then the program will calculate the correct height. Moreover, I also included a figure for depreciation so in order to calculate the total cost during the period of use, then you have to ask depreciation equal time in years that you hold your pump. The cost watts was set at 0.22 euro / kwh possibly changed. Each pump shows the following: The name, the flow in liters, the prevalence in cm, consumption stated in watts and the approximate cost that I found with a quick search without pretense of perfection. The program now calculate the actual flow as discussed above for each pump reported in the spreadsheet under standard conditions. If you had the external pump, or where there is a multiple power such as that for any chiller I suggest putting the percentage of correction to at least 30%. There are also other sensitive data such as the efficiency of the pump, and that is how many liters are handled per watt (it is unnecessary to think that efficiency should be maximum), the same as those of the euro we want to pump a liter, a sort economic efficiency but weighed only on the cost of the pump. Then the cost of annual maintenance, the total cost during the years under variable defined on depreciation years and cubic meters handled in the same period. Now the total efficiency index, which takes into account the actual flow, cost of purchase and maintenance cost, and tells us how many cubic meters we can handle every euro we are going to spend. The file then will present the flow chart for all the pumps considered: The last point concerns the possibility of maintaining the return pump connected to an uninterruptible power supply in the event of interruption of electricity. Having tried on my own tank two systems of this kind of an APC UPS from 800VA, and the Zeus of Ocean Life with battery with 24V and 40Ah, I reported the autonomy of each pump with the two systems tested. The calculation was done simply scaling the real lasting of my system during such simulated events with consumption declared by the various pumps, so it’s certainly a consideration of what can be happen, but that may provide an idea of the duration of the various pumps with 2 UPS into market, for further consideration referring to the two presented link. ATTENTION: All the data were considered as proposed by the manufacturers and extracts from the site and the file must be considered largely theoretical, it would be interesting to have all the pumps, and possibly others, in order to measure the flow and prevalence, so I can update the data presented in this article with real data and measured. To download the file you have to click on below (english version of the file): You can find all the pictures and the spreadsheet here: http://www.danireef.com/2008/11/29/pompe-d...w/#returnpumps3 Recommendations size of the return pump: The data that we need for proper sizing is essentially only one, namely the maximum of treatable water skimmer, the assumption is that the skimmer is enough for our tank. In general, skimmers can be adjusted between a minimum and a maximum flow, we should rather size everything for maximum capacity of the skimmer. Similarly, it would be wise not to rely only to technical data because the reality, especially for a subject as complex hydraulically skimmer, is usually quite different. If a particular brand claims to want a feed pump skimmer of 1,000 liters per hour should measure the actual flow within the skimmer because there’s a pressure drop that would lower the nominal data. We must now decide how much flow tank-sump we want. There are different schools of thought on this issue, those who prefer less, those who prefer more, I’m on the side of those who prefer a more water than skimmer handle. The reason is quite simple, from my personal point of view. To obtain a regular operation would be better that sump and tank have the same concentration of pollutants, and there is no doubt that if all the water that fell in sump were treated by the skimmer we have the coincidence of the two flow. Why deal more? Because if we consider the pressure drop and the fact that the mixture of water don’t ensures that all the water that falls is then treated, is slightly better abound, say at least 10%. Why someone says to treat less? Some claims that it is much better deal less, because in this way the water in sump will be skimmered more time obtaining a better result. This, again from my humble point of view, I think it is physically and economically absurd. It’s absurd because if the sump is “working” at a greater speed we would be an impoverishment of the pollutants in sump, not balanced by water comes from the tank, and the skimmer would work worse and with more effort. Indeed it is physically much more difficult to extract something from a liquid when its concentration decrease. Also over the course of time there would be a stalemate because we always cleaner water in sump (up to a certain limit of course) and even the little water that falls into sump were treated well, we would have a system sump similar to a large skimmer, limited from the flow of the return pump. The concept is not the most simple, and I hope to have been sufficiently clear. Simplifying my thought, if we are in position to have a skimmer more powerful than our return pump mean that we could use a lesser powerful skimmer. Moreover, a bigger flow is useful as a contribution to the movement, especially in the case of LPS or soft corals, and provides a minor effect of the sump towards the tank in all those situations that you can have, like using a chiller. This article is been published on italian monthly magazine Acquaportal and you can read there by clicking on the following image You can find all the pictures and the spreadsheet here: http://www.danireef.com/2008/11/29/pompe-d...w/#returnpumps3