design

I would suggest that you don't reinvent the wheel - that is "design" a heat exchanger; there are many standard off-the-shelve heat exchangers that will work for you, all you need to do is provide a supplier with a few process conditions (temperatures and flows)

Where I work we use quite a few of these API/Basco water cooled heat exchangers for oil applications:

http://www.apiheattransfer.com/us/Products/HeatExchangers/ShellAndTube/Type500.htm

Depending on your location - I would just contact a supplier and work with them to supply an appropriate cooler.

I have seen a few of what I would have considered "home brewed" heat exchangers.

American La France used coils of copper tubing to cool the water pump transmission.

Walter Truck used larger coils of copper in the water tank to keep water from overheating when not discharging.

I believe an engineered heat exchanger would be more efficient, and trouble free than trying to fabricate one yourself.A heat exchanger directly after the hydraulic pump would have the best effect, as the fluid would have less chance to heat the surrounding area. But where are you going to send this removed heat. You could preheat your hot water inlet, but what about when the hot water is not used, and the press is. This is going to need to be addressed.

If your hydraulic press pump is 10 KW, find or buy and 10 or 12 KW oil to air radiator or heat exchanger. Make sure radiator is rated for oil pressure 150% of pump output pressure. Tell supplier of radiator the air supply is 30ºC, and the oil temperature must leave at 40ºC.

Install a supply air fan, filter, and duct to connect the inlet side of the radiator or heat exchanger or radiator. Install exhaust duct and fan to remove hot air from radiator to out doors.

Good answer, I had only considered oil to water. An added benefit should be a cooler shop.

That was part of my thinking. Since HUMA is in Pakistan, I assumed limited and poor quality water. In oil to water heat exchanger, that can lead to fouled and plugged water side on the heat exchanger.

Air to oil heat exchanger should be a bit oversized to deal with warmer air temperatures. If it gets dirty it could be blown out with compressed air. Exhausting the hot side to outdoors would get the heat away from employees.