If I refuel during race, should i refuel while training

In general, if you plan to do something during a race, you should try to simulate it during training. 

That being said, your body likely doesn't need that much "refueling" for a sprint tri of the distance you describe.  Maybe a little water or sports drink and you should be fine. 

You want to train like you race.

That said, a Gu every 30 minutes seems like way too much.  In a sprint (which takes me 1.5 - 2 hours) I will have a Gu about 15 mins before the swim, and another near the end of the bike.  Otherwise just water.  Some do water only since sprints are fairly short.

Yes.

You need to learn how your body will react to the nutrition during training.  You'll also get a better idea of how much/how often you'll want nutrition.  For most people gu every 30 minutes would be too much.

+1.

1 gel mid to late on the bike ought to be enough. Some won't need any. A single bottle of water should be fine, gatorade if it works for you. It's better to go with less than you think on these. Too much or the wrong thing and it'll upset your stomach. If you've trained well you'll have the energy to get through it strong.

My advice is to practice the fueling in training until you're satisfied with the results.   This is my main use of brick workouts.  I try to take enough on my bike ride to feel pretty good for the run.  If I start a post-ride run in training and feel bad, I have to work on the fueling.

If you've got it worked out, and can competently take a gel while riding your bike (for instance, without falling over...) then you can go back to whatever you'd do for a single workout.   I usually don't take anything but water for anything under an hour, but that's personal.  

As far as how many/much/what to take, that's up to you.  I need a bit more than the average person it sounds like, so I take a gel about every half hour, 40 mins max, during a race. 

x2 

As others have said, what you do in you training should dictate what you do in a race.

I'm usually good for about 1-1/2 hours without re-fueling.  Less than that, just some water or Gatorade if it's hot.

For sprint tri's I just take one bottle of Gatorade on the bike and seldom finish it all.  I always try to be well-hydrated before I start a race; I'll sip water or Gatorade up until I get into the water to warm up.

Mark

I carry enough water and food that I don't have to stop. 50 mile rides will take no more than 2 water bottles, and could just as likely be 1 for me depending on the weather and effort level. 1 powerbar will also do, but I'll carry a little more just in case.

Under hydrating is possible, especially with heat involved, but underfueling is more likely pacing vs fitness. Could be just getting used to going for that long. I've done 5:40 on zero fuel, but plenty of water, and there were some solid efforts in there with the hills.

Some of it depends on what your goals are. Many people use nutrition as an excuse to pound down the calories while exercising, and wonder why they never lose weight. If you are trying to get to a racing weight, limiting calories during exercise (and other times) will help.

For a race where you're going to take in calories, it's a good idea to practice a few times by taking them in while training. This doesn't need to be a constant thing, however. Doing it a few times to make sure you can tolerate whatever it is you're ingesting is usually fine. If you're doing anything shorter than an olympic distance (typically less than 1.5 hrs), I don't think it's worth bothering with nutrition. Same goes for training. Beyond that, you may want to introduce a small amount of nutrition depending on time and intensity. Keep in mind, it can be tough taking in nutrition during very intense efforts so what works during training may not be so palatable in a race.

Also remember that the meal you eat before you start exercising counts as nutrition. Typically the only time you start out on empty is if you work out in the morning prior to eating/drinking anything besides water.

Personally, I rarely eat/drink anything except water until the run gets over 12 miles or the ride goes over 2 hours with some good intensity. I've had to work my way up to this though. I used to eat bars and gels, drink a carb/electrolyte drink, and have something for recovery afterwards all in the guise of 'fueling'. All I was really doing was eating empty calories based on what nutrition companies told me to do. I might as well have been drinking beer. After stopping the nonsense, I was able to lose weight much quicker, am able to go longer without requiring nutrition, and recover the same or faster than before. I'm also lighter, fitter and stronger. Lighter everywhere except my wallet, that is.