August 28, 2002

The Arecibo Observatory, operated by Cornell University for the National Science Foundation, wants to add an oil cooler to its radar transmitter. The unit will used to cool 1800 gallons of oil contained in a tank open to atmospheric pressure. The system should consist of a. an oil pump with motor and b. a radiator with fan and motor.The cooling system should be able to dissipate 854 BTU/min (the 15kW of heat transferred to the oil by the electronic equipment in the tank).

We expect that this system will use a fan motor of about 1 hp, a pump to produce a fllow rate of about 12 gpm, and a radiator about 3ft x 3ft.

Data for this application are as follows:

Inlet temperature: 120 degrees F

Heat rejection rate: 854 BTU/min (15kW)

Ambient air temperature: 86 degrees F

Distance from tank to radiator location: approx. 30 ft. (60 ft round trip)

Proposed connection pipe diameter: 2 inches

Site elevation: 1000 ft

Ambient atmosphere: tropical marine

Useage: approx. 150 hours per month

Oil characteristics:

Type: Texaco Transformer Oil Inhibited Code 1515

Viscosity: 8.9 cSt at 40 degrees C

57 SUS at 100 degrees F

Flash: COC	154 degrees C

Dynamic viscosity is also termed "absolute viscosity" and is the tangential force per unit area required to move one horizontal plane with respect to the other at unit velocity when maintained a unit distance apart by the fluid. In SI units the theoretical unit is the Poise. As these units are large, it is more usual to divide them by 100, to give a smaller unit called the centipose (cP).

Kinematic viscosity is the ratio of the absolute viscosity to the density. In SI units, the

theoretical unit is the Stokes. As these units are large, it is usual to divide them by 100, to give a smaller unit called centistokes (cSt), and these are the units used for marine fuel.

Viscosity, SUS : Saybolt Universal Seconds (SUS), which is the time in seconds for 60 milliliters of oil to flow through a standard orifice at a given temperature. (ASTM Designation D88-56.)

Flash Point The flash point is the lowest temperature at which a liquid or solid gives off enough vapour to form a flammable air-vapour mixture near its surface. The lower the flash point, the greater the fire hazard. The flash point is an approximate value and should not be taken as a sharp dividing line between safe and hazardous conditions. The flash point is determined by a variety of test methods which give different results. Two types of methods are abbreviated as OC (open cup) and CC (closed cup). COC = "Cleveland Open Cup"