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Raptors 113, Warriors 93: NBA Finals-worthy preview? Not on this night

first_imgCLICK HERE if you are having a problem viewing the photos or video on a mobile deviceOAKLAND – The Warriors did not offer an NBA Finals preview. Instead, they displayed regular-season sluggishness.The Warriors fell to the Toronto Raptors 113-93 on Wednesday at Oracle Arena, marking two distinct differences from when they played nearly two weeks ago. Unlike their three-point overtime loss in Toronto that Steve Kerr called “the most entertaining game of the year so far,” the …last_img

Using Total Effective Length in Duct Design

first_imgRELATED ARTICLESThe Fundamentals of Rigid Duct DesignThe Two Main Reasons Your Ducts Don’t Move Enough AirAll About Furnaces and Duct SystemsSaving Energy With Manual J and Manual DKeeping Ducts IndoorsReturn-Air ProblemsSealing DuctsDuct Leakage Testing Today I’m going to explain an important concept in one of the most popular ways of doing duct design. I’ve been writing a series on duct design over at my blog and began with a look at the basic physics of air moving through ducts. The short version is that friction and turbulence in ducts results in pressure drops. Then in part 2 I covered available static pressure. The blower gives us a pressure rise. The duct system is a series of pressure drops.We can divide the pressure drops into two categories: those resulting from the ducts and fittings and those resulting from all of the components that aren’t ducts and fittings (e.g., registers, grilles, filters…). When we subtract the non-duct/fitting pressure drops from the rated pressure rise (total external static pressure) of the blower, we get the available static pressure. That’s the total pressure drop we have available for the ducts and fittings and is what sets our duct pressure budget.What we want to get out of this in the end is the proper duct and fitting sizes. We have a certain amount of available static pressure to use up. If our ducts are too small, we can end up with either too little air flow in the case of a fixed-speed blower (PSC, which stands for permanent split capacitor), or we get the air flow but use too much energy with a variable-speed blower (ECM, which stands for electronically-commutated motor). The first step in finding the proper duct and fitting sizes is to find the total effective length (often called equivalent length), the topic of today’s article. What is effective length?Length is length, right? Why do we need something else called effective length? The answer lies in fittings, those duct components that allow you to take air out of a trunkline, split a single duct into two runs, turn the air, and more.For straight duct sections, pressure drop depends only on the length. Well, that’s the idea anyway. If we use flex duct and don’t pull it tight, the pressure drop will be greater than if it were pulled tight. Texas A&M did a study on the effect of flex duct not pulled tight and the results are astounding. In my article on this research, I showed from their results that a 6″ duct moving 110 cfm when pulled tight will move only about 70 cfm with 4% linear (longitudinal) compression and about 40 cfm or less at 15% compression. (I’ll write more about the effect of different duct types in the HVAC design process later in this series.)For our purposes here, I’m going to assume that the ducts we’re using are either rigid metal or flex pulled tight. ASHRAE now has a duct calculator with options for 4%, 15%, and 30% longitudinal compression, but that’s not for use in designing duct systems. It’s to show how bad existing systems are if the flex isn’t pulled tight or to scare installers into pulling it tight.So, we’ve got straight sections of duct with their pressure drops depending on the actual length. And then we’ve got fittings. Each fitting — whether it’s splitting the air flow, reducing the duct size, or turning the air — will cause a pressure drop. In the duct design process, however, it’s more convenient to categorize these pressure drops by the length of straight duct run that would create the same pressure drop. And that, my friend, is the definition of equivalent length.But wait, you say! You were talking about effective length and now you’re talking about equivalent length. What’s going on here? ACCA’s Manual D uses both terms, although without clearly distinguishing them. From the context, though, here’s what I’ve surmised: The effective length is the combination of actual lengths of straight duct and equivalent lengths of fittings. Most people use the term equivalent length for both, though.Adding up all the lengths and equivalent lengthsBefore sizing a duct system, we have to lay out all the ducts. Below you can see an example of one we did recently. It shows the duct layout with all vents, fittings, air flows, and duct sizes. To find those duct sizes, the software we use (RightSuite Universal) calculates the effective length of the most restrictive run. From the return grille to the supply register in that run, it adds the lengths of the straight runs and the equivalent lengths of all the fittings.Each fitting we choose has an effect on the pressure drop and total effective length (TEL). We can look them up in tables, like the one below showing equivalent lengths for various elbows.The main variables we have to work with for this fitting type are:Radius of the turn (R)Diameter of the duct (D)Number of piecesRound or ovalWhen we choose fittings, we pick them based on what’s commonly available at HVAC supply houses. We also go a little conservative here because we’re doing third party HVAC design and don’t have control over the installation. For example, most of the elbows used in actual duct systems have 4 or 5 pieces. We often choose a 3 piece elbow in our design, though, because it gives us a little slack in the design. If the installer uses the 4 or 5 piece elbow instead, with 5 feet less equivalent length, the actual duct system will be less restrictive than the designed duct system, at least in that part.The total effective length (TEL) is the sum of all those fitting equivalent lengths plus the lengths of straight duct. If you’re doing it by hand, you have to go through the process for every single duct run. Then you choose the one that has the greatest total effective length. You do NOT use the sum of all the ducts and fittings.The last image below is a screenshot from RightSuite Universal showing the total effective length in one of our designs. The lengths of straight sections of duct add up to 36 feet for the supply side and 13 feet for the return side. The fittings add up to 290 feet and 85 feet respectively. This is typical. Fittings dominate when it comes to using up the available static pressure, so you have to choose them carefully. Just take a look at that table of elbows above. If you choose well, you can be at 10 or 20 feet of equivalent length. If you choose that smooth mitered elbow, however, you end up with 75 feet.The next stepOnce you lay out your ducts and choose your fittings, you have a total effective length. But here’s a little caveat: Those equivalent lengths for fittings depend on the velocity of the air, too, and it’s not a linear relationship. There are corrections for that effect, which, as far as I know, aren’t currently built into the software.To summarize:The blower creates a pressure rise to move air through the ducts.It’s rated for a certain amount of air flow at a specific total external static pressure.The ducts, fittings, and other components cause pressure drops.Subtracting the pressure drops for all the things that aren’t ducts or fittings from the total external static pressure yields the available static pressure.The available static pressure is the pressure drop budget you have to work with when designing the ducts.Each fitting has an equivalent length that equates its pressure drop to an equivalent amount of straight duct.When you add up the equivalent lengths of all the fittings and then add that number to the length of the straight sections in the most restrictive runs in the return and supply ducts, you find the total effective length (TEL).The next step in designing a duct system would be to take your available static pressure and figure out what friction rate you have to work with in sizing the ducts. Allison Bailes of Decatur, Georgia, is a speaker, writer, building science consultant, and the author of the Energy Vanguard Blog. You can follow him on Twitter at @EnergyVanguard.last_img read more

Has bone conduction returned to wearables?

first_imgCate Lawrence With the old adage everything old is new again, this certainly seems to be the case for phenomenon bone conduction. Once the darling of hearing aids, it began to show up in the consumer headphone market in the early 2000s. During this time, bone conduction headphones were marketed as safer for long-term hearing than their standard counterparts.Since then, the technology has only really begun to make its presence known again over the last few years.  In simple terms, bone conduction enables you to hear sound through the vibration of the bones of your face — usually the jaw bones and cheek bones. The sound waves are bypassing the outer and middle ear where the eardrum is located, and directly stimulating the inner ear which is our actual “hearing organ.”See also: Seniors getting helping hand from wearablesAs well as hearing aids and headphones, the technology has also been attributed to Beethoven’s ability to write music — even while hearing-impaired — through biting down on his composer’s wand that was touching the piano.Here are a few of the devices that are embedding the technology into wearable devices:SgnlIf you’ve ever had a hankering to be James Bond, your dreams can now become a reality. Innomdle Lab, the first company ever to officially spin off from Samsung Electronics have created Sgnl, a smart strap that enables users to engage in phone conversations simply by placing their finger to their ear. Whether attached to a classic watch or a smart watch, users can enable fingertip communication and a number of additional smart functions simply by replacing the watch strap. Additional smart functions include Call Reminders, Fitness Tracker and Smart Alert.Sgnl’s key technology lies in its patented Body Conduction Unit (BCU), which is capable of transmitting vibrations through the body, which then can be converted to sound. Sgnl communicates with the user’s phone through Bluetooth, and when a voice signal is received, Sgnl will generate vibrations through its BCU. These vibrations will be sent through the users’ hand to their fingertip. When users place their fingertip to their ear, the vibration echoes to create amplified sound within the closed space of their ear and they can speak through the microphone embedded in the Sgnl strap. Overall, very appealing.https://readwrite.com/wp-content/uploads/Demo_Fingertip_Phonecall.mp4 Marlen is a wearable device by Hong Kong based start-up Playtsens for swimmers. The wearable is attached to the user goggle strap at the back of the head and the second piece to the ear piece and it sends you voice feedback using a bone conduction headset, even when underwater. Your pace is reported to you as you swim with no disruption to your swim stroke.In open water swims, your swim performance is captured with GPS. In the pool, motion sensors are used when there is no GPS reception. After your swim, you can connect Marlin to your phone with Bluetooth to review your data and update configurations.It’ll be interesting to see how other wearables incorporate bone conduction. It would be easy to imagine some of these examples employed in traditionally noisy settings such as factories and warehouses. It’s also foreseeable that hearing devices and technology becomes more responsive and customizable as our rapidly aging popular sees a decrease in their hearing quality and clarity.While previous generations may have been content to suffer from poor sound quality, our connected generations are more likely to look to technology to solve the problem. Zungle sunglassesDid you know you can now listen to music through your sunglasses? Well not just any sunglasses but a pair created by Zungle containing bone conduction. These sunglasses enable the wearer to listen to music and answer telephone calls as they can be paired with a smart phone through wireless Bluetooth and a noise-cancelling microphone that lets you make and answer calls. They are chargeable via a hidden USB port.Zungle have received over $1.9 million in funding via Kickstarter, having asked for an initial $50,000.Invisio headsetsWhilst not traditionally a general consumer product, bone conduction headsets are popular in military and police occupations. The headsets are configured to work with both analog and digital radios and can be adapted to work with push-to-talk awitches. They include Kevlar-woven cables for added durability, unique whisper capability, the ability to work under eyewer or gas masks and also the ability to clearly communicate in high noise environments.Google Project AuraThe original Google Glass utilized bone conduction audio, meaning nothing needed to be placed inside the ear. This resulted in a more comfortable headset as well as great situational awareness through being still able to hear. Since Google Glass went rather quiet the division responsible, Project Aura whilst scarce in offering information is believed to be continuing their interest in bone conduction technology.Marlin GPS swimmeter Small Business Cybersecurity Threats and How to… Related Posts center_img Follow the Puck Why IoT Apps are Eating Device Interfaces Tags:#bone conduction#Connected Devices#featured#Google Glass#hearing aids#Project Aura#Sgnl#sport wearables#top#wearables#Zungle Internet of Things Makes it Easier to Steal You…last_img read more