heat output from different halides

[zygote2k]

I am going to place another halide over the other end of tank that currently has only 1 fixure on one end. I'm wondering if there is a great difference in heat output based on the wattage of halides. Does a 250 put out more heat than a 150? The existing light is a 400 and I need more light now and was wondering which one to use. 250 or 150 DE 14k. I'm only trying to illuminate about 20" from the light to the top of the structure.

[gastone]

A watts a watt. A 250w halide bulb operating off of a ballast pushing that bulb at 250w puts off 250w of heat. Similarly, a 100w widget operating at 100w puts off 100w of heat.

 

Garrett.

[flowerseller]

A watts a watt. A 250w halide bulb operating off of a ballast pushing that bulb at 250w puts off 250w of heat. Similarly, a 100w widget operating at 100w puts off 100w of heat.

 

Garrett.

 

Yea, but does a 400w put off 400w of heat?

Do the "math" gas.

[gastone]

Yea, but does a 400w put off 400w of heat?

Do the "math" gas.

 

 

I can only do 1:1 ratios. Even then I get confused!

 

G.

[Origami]

I am going to place another halide over the other end of tank that currently has only 1 fixure on one end. I'm wondering if there is a great difference in heat output based on the wattage of halides. Does a 250 put out more heat than a 150? The existing light is a 400 and I need more light now and was wondering which one to use. 250 or 150 DE 14k. I'm only trying to illuminate about 20" from the light to the top of the structure.

 

 

Generally speaking, yes. But it depends on how much power is actually being delivered to the lamp by the ballast. This can vary by ballast manufacturer and design. Electronic ballasts are very good about delivering the rated power to the load while magnetic ballasts can "overdrive" bulbs, regulating amperage and not power. Joe Burger did a little work in this area that was published in a Reefkeeping magazine article in April 2007. Here's the link: http://reefkeeping.com/issues/2007-04/jb/index.php. I suspect that color temperature also has a bit to do with it as well as light that is well outside the infrared spectrum is probably absorbed as heat less efficiently than that within.

 

Note that depending upon the configuration, color, airflow, reflector, height above the tank, etc., the amount of heat transferred to your aquarium will vary.

[Coral Hind]

I am going to place another halide over the other end of tank that currently has only 1 fixure on one end. I'm wondering if there is a great difference in heat output based on the wattage of halides. Does a 250 put out more heat than a 150? The existing light is a 400 and I need more light now and was wondering which one to use. 250 or 150 DE 14k. I'm only trying to illuminate about 20" from the light to the top of the structure.

 

Instead of explaining or correcting what's been said, I will give you the simple answer. Yes, an increase of wattage of the same types of lamps/ballasts will increase heat via all three forms of heat transfer.

 

I switched from 150W to 250W a year ago over my 75g and there was an increase in heat. It was nothing extreme, just a small noticeable increase. I would not worry so much about the heat but find the one that can give to the growth/color you want for the price.

[zygote2k]

What would be better- 250 or 150?

[gastone]

Instead of explaining or correcting what's been said, I will give you the simple answer. Yes, an increase of wattage of the same types of lamps/ballasts will increase heat via all three forms of heat transfer.

 

I switched from 150W to 250W a year ago over my 75g and there was an increase in heat. It was nothing extreme, just a small noticeable increase. I would not worry so much about the heat but find the one that can give to the growth/color you want for the price.

 

 

I'm always looking to learn something new. Can you elaborate? My position is that 100w of heat from a source is equal to 100w of heat from another source, the source being irrelevant. ie 150w from a metal halide (operating at 150w of course) is no different than 150w of heat from and LED (operating at 150w... of course). Heat being transfered into the room or heat being transfered directly to the water (via a heater for example) doesn't matter... it still has to be accounted for. Of course it's easier to deal with/accept 150w of heat in a 1000 cubic foot room then it is to accept 150w of heat in 10 cubic feet of salt water.

 

Help me out here.

 

Garrett.

[Integral9]

In electrical terms:

1 Watt is the work done when 1 amp flows through a potential difference of 1 volt.

 

In mechanical terms:

1 W is the work done when an object is moving at 1 meter per second against the force of 1 newton.

 

Since the work done uses energy and we have to obey the laws of thermal dynamics, the energy lost from the work is put forth in heat and light. In mechanical terms, energy lost due to work is almost always equivalent to the amount of heat produced. In electrical terms, especially when dealing with light bulbs it's not so easy. The amount of heat vs light produced is measured in lumens per watt. So a 150W HQI bulb will consume that much energy; between 9.5 and 17% of that will be light the remainder will be heat.

 

To answer your question though and assuming all other things to be equal (fillament, ballast, color temp, etc), a 250W HQI will produce 60% more heat than a 150W HQI. It will also produce 60% more light. If you want to increase light output but not increase heat, then you'll have to move to a prototype LED or high efficiency OLED. Sodium bulbs would be better, but they can't produce light in the color temps we demand. At least I've never seen one above 4500K.

 

http://en.wikipedia.org/wiki/Luminous_efficacy

[Coral Hind]

Garrett,

 

The "100w widget operating at 100w puts off 100w of heat" statement is what I do not think is accurate.

 

The wattage rating of something is its consumption of electrical power. Just because something uses a certain amount of watts doesn't mean it produces a proporational amount of heat. Wattage consumption depends on how efficient it is and how much energy is lost via resistance and heat production.

 

It also depends on how the heat created is transferred via conduction, convection or radiation. An example would be a 100w infrared lamp and a 100w visible light lamp. The infrared lamp's wavelength induces thermal vibrations in the atomic structure of the item being heated so it is able to heat the air and object greater then what a visible lamp of the same wattage could do.

 

Another example is a 1000W mircowave and a 1000W toaster. The toaster puts off a lot more heat then the microwave.

 

Check out this kids experiment. At the bottom of the page you will see the difference between two 60watt bulbs.

[jnguyen4007]

Bottom line, isn't it safe to say that if you're comparing apple to apple, then the increase in wattage for the same brand, type of bulb, and ballast will equal to increase in heat output? The only other sure fire way of knowing if the increase in wattage will mean increase in heat is to try it out and take a temp measurement.

[gastone]

I can't get there from here.

 

And I can't access that page from work (silly firewalls).

 

I'll have to wait until I get home to educate myself.

 

Garrett.

[gastone]

You guys should all be afraid that I am the one educating your kids...

 

I'm under the (dis)illusion that heat and light are the same thing (energy???). You guys need to remember to use small words when you talk to me.

 

Okay, so if I were to put a 250w lamp over my tank operating at 20% efficiency, and was somehow (we are on fantasy island remember) able, with complete efficiency, prevent the other 200w of heat (energy not emitted as light) to enter the tank, that the 50w of light (presumably) would not effect the temperature of the tank???

 

If you guys get tired of me, feel free to recommend some low level reading and I'll try that on for size.

 

G.

[Origami]

Garrett, heat and light are both forms of energy, but they are not the same. Heat is the energy contained in the motion of atoms and molecules, light is, in the most general sense, electromagnetic energy. Some portions of heat can be transmitted in the electromagnetic spectrum (such as infrared) and that's one principle through which we can measure temperature remotely. It's also one reason why we can feel the heat of the sun despite 93 million miles of vacuum between us (where direct conduction of molecular vibration can't cross).

 

Insofar as the nitpicking of heat transfer that some of us engineers have been engaging in, it's a matter largely of conducted / convected and radiated heat transfer. Heat conduction is occuring via the air to the water. Radiated heat transfer would come from the electromagnetic radiation (light, in this case) being transferred from the lamp.

 

Take this example for a moment. Place a white car and a black car out in a sunlit parking lot. Which gets hotter? Both are in the same environment at the same ambient temperature but the black car gets hotter. Why? The primary difference is the absorbtion of radiated heat. The black car absorbs more of radiated energy while the white car reflects it.

 

Similarly, all colors of light are not equally absorbed by all surfaces, especially when some of those surfaces may be biologically tuned to absorb certain wavelengths of light. The bulb, of course, comes into play here. All bulbs are not equally efficient and produce, among other things, different levels of UV which is often filtered out by the bulb envelope or a glass shield.

 

I'm just kind of winging it here but I hope it makes sense. Generally speaking, 250W in = 250W out, but heat transfer is not always 100% efficient. It rarely, if ever, is. If it were, our energy problem would be solved.

[Coral Hind]

Garrett,

 

So you are asking if we take the remaining light which was made from the 50w of power that was not lost in the production of the light, would that still transfer heat into the tank.

 

I would say yes, the light would still induce heat because of the nature of light. Light is basically electromagnetic radiation in three forms, infrared, ultraviolet, and visible light. Light is made of both particles or protons and waves. As they travel and impact atoms they cause the atoms to vibrate which produces the heat.

 

Even if you remove the luminous flux from the radiant flux the luminous or visible light by itself would still have the ability to heat things up, but it is extremely weak without the radiant flux.

 

A good example of light or luminous flux without radiant flux is a glow stick or lighning bug. They work off of chemoluminescence which does not have the radiant flux that electroluminescence has and therefore doesn't have the heat generating properties.

 

As for your statement of heat and light being the same thing, energy. They are termed as energy but I think of them being more of a mechanism to transfer energy from one mass to another then actual energy themselves.

Edited November 7, 2008 by Coral Hind

[Origami]

Okay, so if I were to put a 250w lamp over my tank operating at 20% efficiency, and was somehow (we are on fantasy island remember) able, with complete efficiency, prevent the other 200w of heat (energy not emitted as light) to enter the tank, that the 50w of light (presumably) would not effect the temperature of the tank???

 

Put a vacuum between the two and that 200W (of non-radiant energy) won't transfer.

 

As for the question, the 50W of light will only convert to heat insofar as the materials which absorb can efficiently do so. Remember the black and white cars in the parking lot.

Edited November 7, 2008 by Origami2547

[gastone]

The sun was my next question....

 

You guys are good. Thanks for taking them time with me. Of course I'll have to spend some more time digesting, and reading wikipedia before it hits home... but I honestly think we are getting there.

 

G.

[Integral9]

You guys should all be afraid that I am the one educating your kids...

Only if you are a physics prof.

Okay, so if I were to put a 250w lamp over my tank operating at 20% efficiency, and was somehow (we are on fantasy island remember) able, with complete efficiency, prevent the other 200w of heat (energy not emitted as light) to enter the tank, that the 50w of light (presumably) would not effect the temperature of the tank???

The 50W of light would increase the temperature of the tank in the same way you feel the "heat of the sun" on your skin when you step out from the shade.

 

There are basically 3 kinds of heat transfer, Radiation, Conduction & Convection. The later two are basically the same, imo with a minute difference. Conduction is the process of heat transferring from a substance directly to another through direct contact. Like when you put your hand on a hot stove burner. OUCH! Convection is the transfer of heat from one substance to another through air or water or some other fluid-like substance. Like putting your hand over a hot stove burner. You know if that burner is warm, but it takes a second for the heat to reach your hand because it has to travel through the air in between. Radiation is the only method of heat transfer that can occur through a vacuum as it doesn't rely on any other substances or direct contact to transfer the heat. Thermal Radiation is often referred to as infrared as those are the most common wave lengths of energy that transfer heat. All wavelengths of light transfer energy (eg. your microwave) and thus heat, it's just that infrared light is the most common and does a bang up job of it.

 

I suspect most of the heat transfer from the light to the tank occurs via convection and of course through radiation. However, in your example, only 20% of the lamps energy consumption is converted to light, thus only 20% of the heat is in the form of light or radiation. For convection, the lamp warms the air around it which causes thermal convection. The warmed air them in turn, warms the objects around it, including the tank. Placing a barrier (acryllic or glass cover) between the light and the tank helps to reduce this. However if the barrier is on the tank, it also prevents the water in your tank from cooling as much as you are reducing the evaporation rate. Also, eventually the barrier will warm up (unless it's insulated) and cause it's own thermal convection between it and the tank. Thus all the pumps and heaters, etc in your tank that produce heat, will cause the heat to build up in the tank. That's why people see their tank temps rise when they put the versa-tops on.

 

You don't want to reduce the thermal radiation if you don't have to. It's what makes our corals will grow, so you only want to reduce the transfer of heat through thermal convection. You can place a fan between the light and tank which will cool the tank and light, or if you can, close the light box and put fan on it to exhaust the heat out of the light box away from the tank. I prefer cooling both as there is less chance for failure. You can also move the light further away from the tank, but that reduces the intensity of light by the square of the distance.

 

My 30 gallon has a ~250W of light (1 x150 HQI, 4x24 T5). The tank has an acryllic cover on it (suicide prevention) and the lamp sits about 12" above the tank. The tank regularly reaches 80-82. The lamp also has a fan inside of it and acryllic and glass covers under the bulbs. When I first put the light over the tank, I hung it about 6" from the water. The temp shot up to 90. Having no other way to reduce the heat (since it was mostly thermal radiation, not thermal convection), I had to push the light further from the tank or risk loosing some expensive fish.

 

My 55 gallon has ~200W of light (4x54 T5). The tank is open on the top and the hood is open in the back. There are 2 5" fans on either end blowing across the tank and bulbs. The tank stays about 75-77 unless the room warms up.

 

If you guys get tired of me, feel free to recommend some low level reading and I'll try that on for size.

G.

I'm not tired of you, but I found this book to very helpful. I don't know if it's still in print though. It's kinda old, Copyright is 1998.

"Hot Air Rises and Heat Sinks, Everything You Know About Cooling Electronics is Wrong" by Tony Kordyban. Good book to help you understand how to keep things cool and a little about thermal dynamics. From the ASME (American Society of Mechanical Engineers) Press. I found it fun read too as the author puts it in perspective of his real-world experiences @ Tellabs Operations.

[gastone]

I looked for the book Friday before I left work. It goes for roughly $150 new... and used ain't easy to find, though I believe I saw it for north of 50.

 

G.

[zygote2k]

I've decided to go for the least amount of heat for the most amount of light: 150w 14k.

Now I know whom to ask for direct questions about thermodynamics.

Thanks.

Edited November 9, 2008 by zygote2k