Domestic Water Heating Flashcards by Lanz Godwin Lacambra

___________ is a heat transfer process
that uses an energy source to heat
water above its initial temperature

Water heating

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Energy consumption for heating
domestic water is the second largest
energy user (after space heating) in the
residential sector in industrialized
countries, accounting for about _____ of
the energy used in a typical household.

14%

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an appliance that heats water for
domestic or building service hot water use

WATER HEATER

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use their fuel to run a burner;
they have burners on the bottom of the
tank and a vent that passes up through the
center of the tank

NATURAL GAS

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uses liquid petroleum gas as its fuel source to heat water for household use;
used in homes that are not connected to natural gas
line, rural areas, or with high electricity cos

PROPANE (LP)

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uses fuel oil as its fuel source instead o f gas or
electricity to heat water for household use;
used in homes that have access to oil delivery

FUEL OIL

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uses electricity to heat water in a storage tank;
have coil-like elements that extend into the tank;
heats water as electric current passes through

ELECTRIC

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consists of a storage tank and a heating
medium;
stores water for use on demand

STORAGE TANK
WATER HEATER

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a _________ serves as control of heating
medium

thermostat

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___________ is insulated to reduce standby
losses

storage

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3 TYPES OF HEATERS

1.) Residential 2.) Commercial 3.) Ultraefficient Water Heaters

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designed for the residential
market;
manufactured at large;
relatively inexpensive and
widely available;

Residential

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similar to residdential;
available with much higher
gas input ratings and
larger storage tanks
also feature larger pipe
connections and such that
can’t be found in
residential types.

Commercial

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use power burners and
enhanced heat
exchangers to force hot
combustion gases into
chambers;
vented with plastic pipes
that go through an outside
wall;
draw combustion air
directly from outside

ULTRAEFFICIENT
WATER HEATER

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aka tankless water heaters or demand
water heaters;- have a heating device that is activated by
the flow of water when a hot water valve is
opened

INSTANTANEOUS
(TANKLESS) WATER
HEATERS

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consist of a separate storage tank whch
stores water heated by a heat exchanger

CIRCULATING WATER
HEATERS

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uses a building’s space heating boiler to
also heat water

TANKLESS COIL AND
INDIRECT WATER
HEATERS

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no separate storage tank is needed;- works best during colder months and is
less efficient during warmer months;

Tankless Coil Water Heater

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requires a separate storage tank;- heated water flows to an insulated storage
tank in indirect water heater.

Indirect Water Heater

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extract energy from outdoor air and use it
to produce hot water very efficiently;- use an electric motor to run a compressor- makes economic sense in hot humid
regions where natural gas is unavailable,
electric energy cost is high, and the need for
dehumidification is constant

HEAT PUMP WATER
HEATERS

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includes collectors mounted in the roof or
in a clear area of the yard, a separate
storage tank near the heater at home,
connecting pipes, and an electronic
controller

Solar water heaters

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_________ preheats the water before it
reaches the water heater

solar system

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a device that injects a controlled amount
of water into a steam flow to lower the
temperature of the steam.- has two types: direct and indirect contact

DESUPERHEATERS

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process of restoring superheated steam to
its saturated state through temperature
reduction

DESUPERHEATING/STEAM CONDITIONING

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found in many medium and large commercial buildings; rare in some residences; continuously circulates hot water from the water-heating unit back to the water heater; ensures that hot water is always available at the taps; avoiding the need to run water for a long time to obtain water at the desired temperature.

HOT WATER RECIRCULATING SYSTEMS

water is constantly recirculated from the water heater through the piping; best for buildings who always have occupancy throughout the day;

CONTINUOUS RECIRCULATING

uses an electronic or electro-mechanical timer to shut off circulation of hot water when there are no occupants

TIMED RECIRCULATING

relies on a sensor located at a remote location in the recirculating line

THERMOSTATICALLY CONTROLLED RECIRCULATING

Forsingle- and two-family dwelling units, this peak occurs during the _______ or _______.

morning or early evening

Residential water heaters are typically sized based on their firsthour rating (FHR)

Residential water heaters

The ________ is the sum of the “standby” hot water found in the tank plus the capacity of the heater to heat water during that first hour.

FHR

________ is taken as 70% of the tank capacity

standby water

A ____________ is rated at 3000 to 4500 watts, which would be a recovery rate of about 12 to 18 gallon per hour.

common residential electric water heater

The recovery rate of a ___________ is typically about double the rate of electric-powered units having the same storage tank size

gas-fired water heater

_________ is the quantity of water that the burner or element can heat to a 100°F(38°C) increase in one hour.

Recovery rate

Average gas-fired residential and light commercial heatersizes fall in the range of _______ to _________, which equates to a recovery rate of about 27 to 68 gallons per hour.

30 000, 75 000 Btu/hr

For a natural gas-fired water heaters, multiplying the burner input rating by ______can approximate recovery rate

0.0009

___________ are selected based on the amountof hot water needed to meet the design load (peak instantaneous demand), in gpm or L/min, at a specific water temperature rise and other criteria

Instantaneous water heaters

The _________ (the flow rate of the instantaneous waterheater) is determined by adding flow rates of fixtures used simultaneously

design load

A good assumption in design of instantaneous water heaters is that that the incoming potable water temperature is no warmer than ______ (______)

50°F (10°C)

A temperature of __________ (_______) should be used in cold climates.

35° to 40°F (2° to 4°C)

Water must typically be heated to _______ for most residential uses.

120°F (49°C)

An approximation method used to determine hot water demand in large multifamily buildings units is based on the_________

demand unit (DU).

Selection of economical sizes for the piping and the meter is based on the __________ for water

total demand

a mechanical device used to move a fluid by converting mechanical energy to pressure energy called head.

PUMPS

are designed to ensure that any pumping action is forward (positive). Its internal design ensures and prevents fluid from recirculating back towards the pump inlet, or within its casing.

POSITIVE DISPLACEMENT PUMP

made up of an outer casing that has a rotating wheel-like component called an impeller inside a stationary cavity created by the casing and called the volute.

CENTRIFUGAL PUMP

The number of _______ determines the number of stages of a centrifugal pump.

impellers

has just one impeller and is better for low head service.

Single-stage pump

has two impellers mounted in series for medium head service

Two-staged pump

has three or more impellers mounted in se ries for high head service such as in deep well pumps

multi-staged pump

a gearbox allowing the connection of an internal combustion engine to one or more hydraulic pumps are driven by a drive, usually an electric motor in building plumbing systems

PUMP DRIVES

it is on the same shaft as the pump impeller; that is, the drive and pump are directly connected.

Close Coupled

minimize vibration and wear between the pump and pump drive, especially for large pumps.

Flexible Coupled

___________ drives are drives designed to operate at a specific speed

Constant speed

have separate speed settings (e.g., high, medium, and low) so they can be adjusted to control speed and, thus, pump flow rate.

Multispeed Drives

provide speed control over a continuous range. It control pump speed by changing the speed of the driver and thus flow rate.

Variable-speed Drives

_____________ installations need to be secured well for vibration and sound control.

Pump-drive

the types of pumps used in a system or the arrangement of pumps in a system. for some pumping installations it may be necessary to use multiple pumps to meet design requirements.

PUMPING CONFIGURATIONS

entails installing two pumps side by side in a piping system

PUMPING IN PARALLEL

involves installing two pumps one in line with the other in a single pipe in a piping system

PUMPING IN SERIES

the flow rate at which liquid is moved or pushed by a pump to the desired point in the system.

PUMP CAPACITY (Qpump)

a pressure difference, expressed in feet (meters). represents the measurement of the height of a liquid column that the pump can generate from the kinetic energy imparted to the liquid.

TOTAL DYNAMIC HEAD (ΔPTDH)

the actual horsepower delivered to the pump shaft under stated operating conditions of the pump where horsepower is 550 foot/pounds per second

Brake Horsepower (BHP)

pump output delivered by the pump

Water Horsepower (WHP)

The ___________ is the operating condition at which a pump most efficiently converts shaft power to flow.

best efficiency point (BEP)

An industry design standard used to approximate the lowest performance level of a pump is an efficiency of _______

55%

The difference between inlet pressure and the lowest pressure level inside the pump. expressed in height, as feet or meters

Net Positive Suction Head

is tied to the rotational speed of the drive (motor). It is expressed in revolutions per minute (rpm)

Pump Speed (N)

are scientific relationships that describe changes in pump capacity, total dynamic head, and BHP when a change is made to pump speed, impeller diameter, or both.

PUMP AFFINITY LAWS

GRAPH THAT SHOWS THE FLOW RATE THAT A SPECIFIC PUMP MODEL AND IMPELLER SIZE IS CAPABLE OF PUMPING OVER A RANGE OF PRESSURE DIFFERENCES. THE PUMP CURVE ALSO SHOWS PUMP SPEED (IN RPM) AND OTHER INFORMATION SUCH AS PUMP SIZE AND TYPE, AND IMPELLER SIZE.

PUMP PERFOMANCE CURVE

________ CONTAINS EXCESS CALCIUM (CA) AND MAGNESIUM (MG) IONS. IT IS MEASURED IN GRAINS PER GALLON (GPG), PARTS PER MILLION (PPM), OR MILLIGRAMS PER LITER (MG/L).

HARD WATER

SOFT WATER HAS A HARDNESS OF ____ GPG OR LESS, WHILE HARD WATER HAS ___ GPG OR MORE.

3.5, 7

______________ REMOVES CALCIUM AND MAGNESIUM IONS FROM HARD WATER.

WATER SOFTENING

THE MOST COMMON METHODS USED IN RESIDENTIAL SETTINGS ARE

ION EXCHANGE REVERSE OSMOSIS.

HARD WATER PASSES THROUGH RESIN BEADS WITH SODIUM OR POTASSIUM IONS. CALCIUM AND MAGNESIUM IONS ARE EXCHANGED FOR SODIUM OR POTASSIUM IONS. AFTER SATURATION, RESIN BEADS ARE REGENERATED BY FLUSHING A BRINE SOLUTION THROUGH THEM. THIS PROCESS MAY ADD SODIUM TO THE WATER, WHICH CAN BE PROBLEMATIC FOR INDIVIDUALS ON SODIUM-RESTRICTED DIETS

ION EXCHANGE

WATER IS FORCED UNDER PRESSURE THROUGH A SEMIPERMEABLE MEMBRANE. THE MEMBRANE ALLOWS WATER MOLECULES TO PASS WHILE EXCLUDING IONS AND OTHER SUSPENDED MATERIALS. THESE SYSTEMS OFTEN INCLUDE AN ACTIVATED CARBON FILTER FOR ADDITIONAL TREATMENT. MAINTENANCE INVOLVES REPLACING THE MEMBRANE EVERY TWO TO THREE YEARS AND THE CARBON FILTER ONCE OR TWICE PER YEAR.

REVERSE OSMOSIS