Oil heater
Encyclopedia
An oil heater, also known as an oil-filled heater, oil-filled radiator, or column heater, is a common form of convection heater
used in domestic heating. Although filled with oil
, it is electrically heated and does not involve burning any oil fuel, such as kerosene
.
at the base of the heater heats up the oil, which then flows around the cavities of the heater by convection
. The oil acts as a heat reservoir
or buffer, with a relatively high specific heat capacity (approximately 2 kJ.kg-1.K-1) and high boiling point
(approximately 150-300 degrees Celsius)Boiling Points of some common Fluids and Gases. The high specific heat capacity allows the oil to store a large amount of thermal energy
in a small volume, while the high boiling point
allows it to remain in the liquid phase for the purpose of heating, so that the heater does not have to be a high pressure vessel
.
Using the oil as a heat reservoir
, the heating element
heats the oil, which remains warm for a long period of time while the heat is transferred to the metal wall through convection, through the walls via conduction, then to the surroundings via convection and radiation. The columns of oil heaters are typically constructed as thin fins, such that the surface area of the metal columns is large relative to the volume of the oil heat reservoir. A large surface area allows more air to be in contact with the heater at any point in time, allowing for the heat to be transferred more rapidly from the heater into the room.
, they are still commonly used in bedrooms and other small-to-medium-sized enclosed areas. This is because gas heaters, especially when unflued, are not suitable for bedroom use - gas heaters cannot be used in confined spaces due to the reduced oxygen
and emissions produced. This leaves electrically powered heaters, such as oil heaters and fan heaters
, as the only alternative.
There are several efficiencies that can be measured in regards to heaters: the efficiency of the heater at converting electricity to heat, the efficiency of heating a room with a given amount of power may also be measured. The efficiency of the electrical generator
which powers the heater and power loss from transporting the electricity over power lines may be measured also. Measures may also consider how well a heater keeps the temperature of a space above a certain point. Such a measure would find inefficiencies in heating an already warm room. Many heaters (the majority of currently available models) are equipped with a thermostat
to prevent this inefficient heating, which in turn reduces running costs compared to heaters without a thermostat
. This feature was much more common in oil heaters than in the cheaper fan heaters
until recently; thus many older oil heaters will be cheaper and more efficient to run than their contemporary fan heaters
that lack the thermostat.
Typical oil heaters range in power consumption/output from 300 to 2400 Watts
, and their length and number of columns is roughly proportional to their power rating. A 2400 Watt
oil heater is usually approximately 1 metre (3.3 feet) in length.
, as they can have lower surface temperatures and require less consideration of the flow of air through/over the heater.
Most modern small heaters have some form of tilt sensor to cut power if they are knocked over or placed on an unstable surface. This can reduce the risk of fire if a heater is knocked over.
The surface temperature of oil heaters is usually low enough to be able to dry items of clothing by hanging them over the heater. Great caution must be exercised as there is a fire risk if the clothing is not removed immediately once it is dry; especially in the case of synthetic fabrics such as polyester
, which can be melted or burnt where they are in contact with the heater. It should also be noted that some oil heaters contain strong warnings to avoid operation in damp areas (such as bathrooms or laundry rooms) because the moisture and humidity can damage components of the heater itself. From a safety standpoint, having any objects within three feet of an oil heater is generally to be avoided, and using one to dry clothes is not recommended by any modern manufacturer.
Even though, in normal operation, the surface temperature of the heater is quite low, the extra thermal resistance of the clothing on the heater can cause its surface temperature to rise in order to maintain the same level of heating for the room.
Some companies offer oil heaters with a fan to encourage air flow over the heater. Since it is constantly bringing the colder air from the room into contact with the heater, this can improve the rate of heat flow from the heater into the room. The rate of heat flow from the heater into the air in contact with it is higher when there is a greater temperature difference between said heater and air.
Convector heater
A convection heater is a heater which operates by air convection currents circulating through the body of the appliance, and across its heating element. This heats up the air, causing it to increase in volume and so become buoyant and rise...
used in domestic heating. Although filled with oil
Oil
An oil is any substance that is liquid at ambient temperatures and does not mix with water but may mix with other oils and organic solvents. This general definition includes vegetable oils, volatile essential oils, petrochemical oils, and synthetic oils....
, it is electrically heated and does not involve burning any oil fuel, such as kerosene
Kerosene
Kerosene, sometimes spelled kerosine in scientific and industrial usage, also known as paraffin or paraffin oil in the United Kingdom, Hong Kong, Ireland and South Africa, is a combustible hydrocarbon liquid. The name is derived from Greek keros...
.
How it works
Oil heaters consist of metal columns with hollow cavities, inside which oil flows freely around the heater. A heating elementHeating element
A heating element converts electricity into heat through the process of Joule heating. Electric current through the element encounters resistance, resulting in heating of the element....
at the base of the heater heats up the oil, which then flows around the cavities of the heater by convection
Convection
Convection is the movement of molecules within fluids and rheids. It cannot take place in solids, since neither bulk current flows nor significant diffusion can take place in solids....
. The oil acts as a heat reservoir
Heat reservoir
In thermodynamics, a heat reservoir, thermal reservoir, or heat bath is a system whose heat capacity is so large that when it is in thermal contact with some other system of interest its temperature remains effectively constant. The heat bath is effectively an infinite reservoir of energy and...
or buffer, with a relatively high specific heat capacity (approximately 2 kJ.kg-1.K-1) and high boiling point
Boiling point
The boiling point of an element or a substance is the temperature at which the vapor pressure of the liquid equals the environmental pressure surrounding the liquid....
(approximately 150-300 degrees Celsius)Boiling Points of some common Fluids and Gases. The high specific heat capacity allows the oil to store a large amount of thermal energy
Thermal energy
Thermal energy is the part of the total internal energy of a thermodynamic system or sample of matter that results in the system's temperature....
in a small volume, while the high boiling point
Boiling point
The boiling point of an element or a substance is the temperature at which the vapor pressure of the liquid equals the environmental pressure surrounding the liquid....
allows it to remain in the liquid phase for the purpose of heating, so that the heater does not have to be a high pressure vessel
Pressure vessel
A pressure vessel is a closed container designed to hold gases or liquids at a pressure substantially different from the ambient pressure.The pressure differential is dangerous and many fatal accidents have occurred in the history of their development and operation. Consequently, their design,...
.
Using the oil as a heat reservoir
Heat reservoir
In thermodynamics, a heat reservoir, thermal reservoir, or heat bath is a system whose heat capacity is so large that when it is in thermal contact with some other system of interest its temperature remains effectively constant. The heat bath is effectively an infinite reservoir of energy and...
, the heating element
Heating element
A heating element converts electricity into heat through the process of Joule heating. Electric current through the element encounters resistance, resulting in heating of the element....
heats the oil, which remains warm for a long period of time while the heat is transferred to the metal wall through convection, through the walls via conduction, then to the surroundings via convection and radiation. The columns of oil heaters are typically constructed as thin fins, such that the surface area of the metal columns is large relative to the volume of the oil heat reservoir. A large surface area allows more air to be in contact with the heater at any point in time, allowing for the heat to be transferred more rapidly from the heater into the room.
Efficiency
Although oil heaters are more expensive to run and provide far less spatial heating than gas heatersGas heater
A gas heater is a device used to heat a room or outdoor area by burning natural gas or liquefied petroleum gas. Indoor household gas heaters can be broadly categorized in one of two ways: flued or non-flued, or vented and unvented...
, they are still commonly used in bedrooms and other small-to-medium-sized enclosed areas. This is because gas heaters, especially when unflued, are not suitable for bedroom use - gas heaters cannot be used in confined spaces due to the reduced oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
and emissions produced. This leaves electrically powered heaters, such as oil heaters and fan heaters
Fan heater
thumb|Typical fan heater's internal partsthumb|Overheat cutoutsA fan heater is a heater that works by using a fan to pass air over a heating element. This heats up the air, which then leaves the heater, warming up the surrounding room...
, as the only alternative.
There are several efficiencies that can be measured in regards to heaters: the efficiency of the heater at converting electricity to heat, the efficiency of heating a room with a given amount of power may also be measured. The efficiency of the electrical generator
Electrical generator
In electricity generation, an electric generator is a device that converts mechanical energy to electrical energy. A generator forces electric charge to flow through an external electrical circuit. It is analogous to a water pump, which causes water to flow...
which powers the heater and power loss from transporting the electricity over power lines may be measured also. Measures may also consider how well a heater keeps the temperature of a space above a certain point. Such a measure would find inefficiencies in heating an already warm room. Many heaters (the majority of currently available models) are equipped with a thermostat
Thermostat
A thermostat is the component of a control system which regulates the temperature of a system so that the system's temperature is maintained near a desired setpoint temperature. The thermostat does this by switching heating or cooling devices on or off, or regulating the flow of a heat transfer...
to prevent this inefficient heating, which in turn reduces running costs compared to heaters without a thermostat
Thermostat
A thermostat is the component of a control system which regulates the temperature of a system so that the system's temperature is maintained near a desired setpoint temperature. The thermostat does this by switching heating or cooling devices on or off, or regulating the flow of a heat transfer...
. This feature was much more common in oil heaters than in the cheaper fan heaters
Fan heater
thumb|Typical fan heater's internal partsthumb|Overheat cutoutsA fan heater is a heater that works by using a fan to pass air over a heating element. This heats up the air, which then leaves the heater, warming up the surrounding room...
until recently; thus many older oil heaters will be cheaper and more efficient to run than their contemporary fan heaters
Fan heater
thumb|Typical fan heater's internal partsthumb|Overheat cutoutsA fan heater is a heater that works by using a fan to pass air over a heating element. This heats up the air, which then leaves the heater, warming up the surrounding room...
that lack the thermostat.
Typical oil heaters range in power consumption/output from 300 to 2400 Watts
Watt
The watt is a derived unit of power in the International System of Units , named after the Scottish engineer James Watt . The unit, defined as one joule per second, measures the rate of energy conversion.-Definition:...
, and their length and number of columns is roughly proportional to their power rating. A 2400 Watt
Watt
The watt is a derived unit of power in the International System of Units , named after the Scottish engineer James Watt . The unit, defined as one joule per second, measures the rate of energy conversion.-Definition:...
oil heater is usually approximately 1 metre (3.3 feet) in length.
Safety and features
In general, oil heaters are considered safer than electric fan heatersFan heater
thumb|Typical fan heater's internal partsthumb|Overheat cutoutsA fan heater is a heater that works by using a fan to pass air over a heating element. This heats up the air, which then leaves the heater, warming up the surrounding room...
, as they can have lower surface temperatures and require less consideration of the flow of air through/over the heater.
Most modern small heaters have some form of tilt sensor to cut power if they are knocked over or placed on an unstable surface. This can reduce the risk of fire if a heater is knocked over.
The surface temperature of oil heaters is usually low enough to be able to dry items of clothing by hanging them over the heater. Great caution must be exercised as there is a fire risk if the clothing is not removed immediately once it is dry; especially in the case of synthetic fabrics such as polyester
Polyester
Polyester is a category of polymers which contain the ester functional group in their main chain. Although there are many polyesters, the term "polyester" as a specific material most commonly refers to polyethylene terephthalate...
, which can be melted or burnt where they are in contact with the heater. It should also be noted that some oil heaters contain strong warnings to avoid operation in damp areas (such as bathrooms or laundry rooms) because the moisture and humidity can damage components of the heater itself. From a safety standpoint, having any objects within three feet of an oil heater is generally to be avoided, and using one to dry clothes is not recommended by any modern manufacturer.
Even though, in normal operation, the surface temperature of the heater is quite low, the extra thermal resistance of the clothing on the heater can cause its surface temperature to rise in order to maintain the same level of heating for the room.
Some companies offer oil heaters with a fan to encourage air flow over the heater. Since it is constantly bringing the colder air from the room into contact with the heater, this can improve the rate of heat flow from the heater into the room. The rate of heat flow from the heater into the air in contact with it is higher when there is a greater temperature difference between said heater and air.