My Kia Sportage 2009 Diesel is periodically making a loud noise with I assume a fan that sounds like it's right behind the dashboard on the passenger side. please help

Is this vehicle new to you? Does this only make this sound when accelerating, leaving a green light or kicking into passing gear? If so, it is probably your turbocharger which, by the way, is actually 2 fans and could possibly be located near the firewall on the passenger side. A turbo charger is driven by a fan that is in your exhaust pipe line which drives another fan that forces more outside air into your combustion chambers, AKA, cylinders. A turbocharger will give what is naturally a sluggish diesel engine more pep and git up and go. It will make a difference on race day if installed on a gasoline engine. This is what causes the high pitched whine coming from the engine of a tractor trailer when the driver gets on the pedal. At idle on a passenger vehicle, it can cause kind of a low growling or yawning sound under the hood. At idle, you don't need all of that extra air in the engine so a dump gate opens and vents that clean air back into the atmosphere. On a tractor trailer driving at 70 MPG, the "turbo" can spin as fast as 110,000 revolutions per minute, (RPM). On a passenger car with a stock engine, probably less. Some things to remember that are VERY important.
1) Turbo's, once damaged, are usually not reparable however they are invariably expensive to have replaced. If your engine came stock with one, it will NOT run well without it. Take care of it.
2) As I said before, turbo's are driven by a fan that is driven by your exhaust system and is usually near the engine to keep air tubing runs short and cheap. Every time you piston fires, it generates a blast of heat exiting your engine at 4,000 degrees. This hot exhaust blows on one fan to drive the other fan. This is all in one housing so fans, housing, shaft and bearings get extremely HOT!!!
3) Turbos small oil lines that are fed by your engine oil pump to lubricate the shaft bearings inside. For this, cheap oil will cost you a LOT more than you will save by using the Walmart house brand, Havoline, Dollar General or even Quaker State. I mention Quaker State because my father bought a brand new 1974 Pontiac with a 400 C.I. engine and he religiously used Quaker State Deluxe, their top of the line motor oil because that's what GM said to use. I changed it every 3,000 miles from day one. At 50,000 miles, I noticed that his rocker arm cover gaskets were beginning to leak. I picked up new ones and proceeded to take the covers off. He had hollow push rods that were supposed to bring oil up to lubricate the rocker arms and valve tips that were so clogged that the valve tips were wearing excessively and I had to adjust them. I had to run coat hangar wire down the hollow centers and soak them in gasoline to clear them out. I also had to go in and get a teaspoon to shovel the 2 inches of sludge off from the top of the cylinder heads. From both sides of the engine, I filled an empty quart Quaker State oil can with sludge. I could only imagine what his oil pan looked like inside. Cheaper oils will break down faster and cause more sludge to form than something like Valvoline racing oil, the Castrol premium oils or name brand full synthetics. Even if your turbo only spins at 80,000 RPM, if a chunk of sludge blocks that thin lube tube for just a few seconds, the bearings WILL overheat and lock. You can't fight physics. The inertia of something weighing 2 or 3 pounds and spinning at 80,000 RPM's not to mention that 1/2 inch by 2 inch shaft that is heated to about 1,200 degrees. Now slam on the brakes and come to a halt in 2 seconds or less. All that energy has to go somewhere. It usually goes into making that fan shaft look like a steel peppermint stick and throwing those two fans full of sharp blades slicing their way out of their housing like 2 cats in a zip lock.Trust me when I say that better oil and quality filters are the better investment. Physics 1, you 0.
4) Keeping a clean air filter is just a good investment and I'm NOT referring to those $49.00 oil soaked "washable" messes that they sell at Walmart. Put a handkerchief over your face and breathe. Now soak it in oil, put it back over your face and breathe some more. That's the difference. Those filters, to deliver as much air as a quality dry paper filter, would have to be 4 times larger than they are. They have their place on mud trucks and sand runners but not on a road engine with lungs the size of King Kong but only being fed air from a pocket sized tank. A good, clean paper filter will give you better fuel economy and performance and if the turbo fan doesn't have to fight it's way out of a box full of sand to get a breath of fresh air, it will greatly reduce the stress and fatigue on that 1,200 degree shaft. Again, physics is a son of a gun. Any time you heat metal, ANY metal, it gets a little softer than it is when it is cool. You have 4,000 degree exhaust trying to push it's fan at 80,000 RPM and it's brother fan is working against the vacuum of a dirty air cleaner in an enclosed box and you generate more than an ideal amount of torque on the 2 or so inches of hot fan shaft between the two fans.
Physics 2, you 0. Good luck.