先ほどアップした実験結果の記事に、より正確な流量測定方法などお伝えしました。その実験では、幾つかのモデルではメーカー公表値よりも大きな流量を得られることが分かりましたが、Tunze Stream2 (6105,6205,6305)ではメーカー公表値よりも実測地が大きく下回っていました。
もし、実測値が公表値の15-20%内でしたら、実験時のエラーなどが考えられるとおもいます。しかしながら、結果は30-55%も下回っていました。
確かに、ロープレッシャー、ハイボリュームのぽろぺら型パワーヘッドの測定は簡単ではありませんが、測定自体は可能です。Hydor社のKoralia6,7,8の流量はTunze Stream 6105, 6205, 6305と同程度ですが、Koraliaはメーカー公表値の2%程度しか誤差がありません。Hydor社は、パワーヘッドの分野に参入して比較的新しいですが、公表値と実測値の差が然程ありません。ですので、非常に良い製品を作り出しているTunze社も公表値と実測値の差を少なくすることは難しくないはずです。
Tunze社にとっては実験結果は驚きだったと思います。実験をした人たちは、公表する前にTunze社に結果とコメントを送付したようです。そして今日、Tunze社から実験結果に対する作者への労いの言葉と実験結果に賛同するコメント出しました。Tunze社は、「私達は実験結果が正しいことを受け入れ、既存のユーザーの為に改良を加えます。」とコメントを出しています。
メーカー公表値を出せるように、Tunze社がどのような改良が加えられるのか待ちましょう。しかし、このような実験結果を素直に受け入れ、ユーザーに対して真摯に対応するってところは、さすがTunzeだなと感じます。Tunzeのパワーヘッドの良さは使った人なら分かりますし、あの頑丈さは半端がないですからね。
以下が、Tunzeからのコメント原文になります。
TUNZE
Where did we get our flow numbers?
We derived our flow numbers in two ways, by a test termed a “bag test” and by theoretical calculations. The bag test is just as simple as it sounds, a collapsed bag is placed over the end of the pump and inflated by the pump with water, the time to fill the bag is measured and the flow is calculated. This method has definite limitations, it places backpressure on the pump, and it cannot be used on larger pumps given the limits of bag volume and reliable timing. For all pumps a theoretical calculation is made based on propeller surface area and rotation frequency.
Our bag test results are consistent (within + or – 10%) with theoretical results on the pump models 6015, 6025, 6045, 6055, 6065 and 6085. This led us to rely on theoretical numbers. The biggest pump that a bag test can be performed on is the 6105 and the inaccuracy of flow numbers on the 6105 has a different origin than 6205 and 6305 inaccuracies. The 6205 and 6305 flow numbers were only based on theoretical calculations. The 6105, when released, was near specified flow and was bag tested with a result of 90% of theoretical, however, later modifications to reduce noise relied on theoretical flow numbers and flow was lost to these modifications. On models 6205 and 6305 the fundamental issue is that the theoretical flow cannot be reached due to overly constricted intake and output.
Going Forward.
Over the next 6 months we will perform numerous tests aimed at improving our pumps. We believe pump volume alone does not equal effective flow, the ability to direct that flow is also important. In much the same way as the light available from a bulb means little if it cannot be properly directed into the aquarium, the flow rate at a pump is not as important if there is not sufficient flow at the corals.. We have since purchased two flow meters, one uses comparable sonic technology and the other uses a propeller akin to a common wind gauge and while we have found that using the comparable meter and methodology our results are the same. We have also found the propeller based meter gives divergent data, this data indicates that our more forceful targeted flow draws in current as the distance from the pump increases and that our total flow produced may be well higher than the flow of the pump itself.
Use of a different methodology may very well give the opposite results, but this does not dispute the results of this study, it will only show that flow is complex and has numerous aspects which we are only beginning to understand. At this point we conclude that the study is correct for the flow produced by the actual pump itself and we will improve the pumps in a retrofittable manner, though this will take time as new parts must be designed and produced. Improvements will be based on increasing intake surface and reducing output restrictions on models 6205 and 6305 and increasing rotational speed for 6105. We would like to thank Sanjay Joshi, Bill Straka and Michael Sandford for performing this study, graciously informing us of the results and giving input on proposed solutions. We believe it is a step forward in uncovering many of the mysteries of high volume, low pressure flow which until recently was nearly impossible to quantify.
