Understanding Power Consumption for Heating Oil

When you're studying for the Oilers and Plant Tenders (HHC) Civil Service Exam, grasping practical calculations is crucial. One common question revolves around the power consumption of an electrical heater used to raise the temperature of oil. Have you ever wondered how you'd tackle a question that asks for the approximate power needed to heat 20 gallons of oil by 100 degrees Fahrenheit in just one hour?

Let’s break this down step-by-step, so you’re fully prepared when you encounter something similar on the exam.

First, you’ll want to start with the specific heat of oil, which tends to hover around 0.42 BTU per pound per degree Fahrenheit. It’s an essential figure that nails down how much energy it takes to increase the oil's temperature.

Now, how do we convert gallons of oil into pounds? The conversion is straightforward; each gallon weighs about 7.5 pounds. So, if you have 20 gallons, you multiply:

20 gallons × 7.5 lbs/gallon = 150 lbs.

Now you have the weight to work with! But wait — let’s not lose focus. We need to calculate the energy needed to heat this 150 pounds of oil by 100°F. The formula you’ll be using looks like this:

Energy (in BTUs) = weight (in lbs) × specific heat (in BTU/lb°F) × temperature change (in °F).

Plugging in those numbers gives you:

Energy = 150 lbs × 0.42 BTU/lb°F × 100°F.

Can you guess what that totals up to? That’s right — 6300 BTUs. It’s like turning on the stove and waiting for those pancakes to cook, but here’s the catch: you must convert that energy requirement from BTUs to kilowatts to get the power consumption.

This conversion is where it gets interesting. One kilowatt is approximately equal to 3412 BTUs per hour. So you’ll take the total energy you calculated (6300 BTUs) and divide it by that 3412:

Power (in kW) = Energy (in BTUs) / 3412.

What do you get when you do the math? You arrive at a power consumption of about 1.84 kilowatts. But don’t get too attached to that number; remember the options provided in your original question: A. 1.3, B. 2.6, C. 3.9, D. 5.2.

Ah! The magic number here is B. 2.6 kW. So, when you gear up for your exam, ensure you understand these calculations. They aren’t just numbers; they’re about getting a job done efficiently — just like a well-oiled machine. And who knows? Understanding this could be the key to acing a question that stands between you and that coveted position.

So, next time someone asks how to figure out the power needed for heating oil, you’ll be ready to tackle it like a pro! Remember that real-world application is something you can showcase not only in exams but in future roles as a plant tender or oiler as well. Keep studying, and best of luck in your exam!