Ch.12,13,14

List three characteristics of air cooled condensers which are considered to be advantages over condensing equipment that uses water

Cheaper, won't freeze unlike water, air is readily available

How can the problem of refrigerant migrating to the condenser from the receiver be prevented

Check valve

What is the basic method used to provide head pressure control on the refrigerant side

Flood the condenser with holdback valve

Cooling tower drift is

None of the above

Algae is?

Plant growth

A recirculating condenser water system having a cool tile removed approximately 1000 BTUs for each pound of water evaporated

1000 btu

The two types of mechanical draft cooling towers are

Induced draft and forced induced

Describe another cold weather problem that can occur during off cycle

Liquid migration to the condenser . Won't make the low pressure switch

Back flooding of the condenser causes the liquid refrigerant to become greatly subcooled which could cause problems with maintaining receiver pressure what two basic methods are used to heat refrigerant sufficiently to prevent this

Liquid throttling valve Hot gas bypass valve

What are six symptoms which appear in a refrigeration system with an air cooled condenser operating at low ambient temperatures and without some sort of head pressure control

Low head pressure Low suction pressure High superheat Short cycling Lack of cooling Liquid like flash gas

Can the single valve Type of backsliding control with a check valve in the equalizing line be used with the condenser at the same level as the receiver

No still would need a pressure differential to remove liquid migration

Cooling towers can be constructed in several arrangements as concerns the relative directions of water flow and airflow three such arrangements are

Parallel flow counterflow and crossflow

How does backflooding of the condenser with refrigerant cause the head pressure to rise

Reduces condenser capacity taking less hot discharge gas to raise pressure of condenser

How does the use of liquid line solenoid valve and pump down operation prevent migration up the suction line to the condenser

Refrigerant ends up in the receiver

How does low head pressure cause the problems listed in the answer to question 1

Starve the evap, superheat will rise

Calling towers contain a number of items which should be clean to assure adequate flow of water through the tower two of these items are

Strainers , spray nozzles

A refrigeration system has an air cooled condenser which is located outside, the remainder of the system being located inside. If the system cycles off during cold weather, the compressor may not start on the next on cycle because

The evap pressure may be to low

When the heat exchanger method of backsliding is used what causes the condenser to flood out low ambient temperatures

The liquid coil in the heat exchanger is designed with a high pressure dropped because of that all the liquid refrigerant can't pass through the coil and into the receiver

Why do you need a receiver when using refrigerant side head pressure control

To flood condenser when head pressure drops, needed for additional refrigerant

Dry coil operation of an evaportative condenser depends on

Transfer of sensible heat

List three methods of using airside control of system head pressure

Two speed fan motors , dampers, cycle condenser fan speed

List three methods of controlling the capacity of air cooled condensers

Two speed motors, dampers, cycle fan,

About how much condenser capacity reduction is achieved with a two speed fan operating at half speed

Two thirds of design

The lowest temperature of water obtainable from a cooling tower is limited by The

Wetbulb temp

What is gained by placing your pressure differential valve in the bypass instead of using a simple check valve

You can keep your receiver at the same elevation as the condenser

The proper location of the cooling tower bleed off is

At the High Point of the piping system