centralized water supply for domestic use overview:
Principle:
1. Supply of appropriate amount of hot water to satisfy users. The selection strives to be scientific and economical.
2. Excessively large-scale selection will cause waste to users.
Elements:
1. The amount of bathing water used depends on the specific scale of the water used (such as the total number of residents in the apartment, the occupancy rate of hotel rooms, etc.).
2. The type of shower used is that the amount of water flow per minute.
3. The length of peak time for bathing water. (The peak period depends on the type of user) As long as the peak period can be met, water consumption during other times can be met.
4. Due to the large amount of water used during peak periods, choosing a hot water furnace will cause waste. Therefore, a matching water storage tank is selected to combine it into a heating water system to ensure water use during peak periods.
(The example in this article takes the water heater produced by A.O.Smith Company in the United States as an example)
Selection and calculation of domestic water:
Known conditions:
(1) The nature of the user and the water usage method must be clear. For example, different users such as apartments, hotels, restaurants, factories, bathrooms (including saunas), the peak hours of hot water use vary at any time. For example:
Most of the hot water used in apartments is concentrated in about two hours before going to bed at night, which is the peak period.
Hotels are mostly concentrated in about two hours at night. For hotels that often organize meetings, it may be more concentrated, about an hour.
Restaurants are mainly concentrated before and after meals.
Factory is mainly concentrated in bathroom opening (off work).
Commercial bathroom, peak hours at night or holidays.
The height of the building and the distribution of water.
In short, you must understand the basic situation of the user, especially during the peak period of hot water use.
(2) The status and number of equipment for water use:
The understanding of equipment and quantity is to reasonably determine whether to use it.
Bathtub: The general bathtub capacity is 150L, among which surfing bathtub has many specifications, and the requirements must be understood clearly.
Shower: If the amount of water required by the user is not required, the household water is generally set at 6-7L/min, and the public bathroom is generally not less than 8L/min.
Dishwasher: Sink or dishwasher, how big is the specifications.
Washing machine:
Example: For general baths, after filling a basin with hot water stored in the hot water furnace of EMGLP-30, it can satisfy the user for a few more minutes after 20 minutes. But for large surfing or jacuzzi, you can only fill one basin and have almost no extra hot water after it is filled. The water temperature is low, and it takes 40 minutes to reach the water temperature for the secondary rinse. Users will not soak in the bathtub for 40 minutes, usually 20 minutes is enough. Therefore, a 50-gallon hot water stove must be selected. After the first release of water, because there is a lot of hot water left and the water temperature is also high, it only takes 20 minutes to satisfy the user's second water supply.
(3) Number of people using water
The number of people using water is the basis for the calculation of the amount of water used, and it is also related to the way users use water. For example, foreign-related hotels and high-end hotels, the standard room often only has one person in two beds. Most of the hotels live together. Especially the number of meeting-type people is more important. For commercial bathrooms and saunas, accurate calculations should be made for traffic.
Calculation program:
Example: A certain public institution 's own hotel: (in use project)
Water usage status: Number of hotel rooms: 50, standard rooms, 100 beds, and the number of occupants at full capacity: 100 people.
water hot water stove is only for water for guests in the room. Others such as restaurant water and laundry water is not included.
Water use time: 24 hours hot water supply
Energy: Natural gas
Calculation:
Calculation according to the daily water use of 130 liters (60℃) for each guest (the unit of self-provided hotels are according to the standards of the guesthouse);
Cold water temperature is calculated according to 5℃;
Maximum water supply per hour, according to the "Urban Water Supply and Drainage Design Manual" or "Engineering Project Selection Manual"
Calculation formula 1
Qh=Kh×m×qr/T Formula 1
where Qh: maximum hourly hot water consumption (L/H);
qr: hot water consumption quota, see Table 1 "Hot Water Consumption Quota", 130L/H, 60℃
m: water calculation unit number (person or bed); 100
T: hot water supply time (h); 24 hours
Kh: hour change coefficient , when supplying hot water for full-time, select according to Table 6 "Hot Water Supply Hour Coefficient Kh Value".
Kh: =7.0
Qh =7.0×100×130/24=3800L/h (60℃)
Selection: A.O.SMITH BTR-500T, commercial gas volume water hot water furnace, outlet temperature 70℃,
Quantity: 2 units, parallel connection;
Hot water tank: open insulation water storage tank, volume 6M3, effective volume 5M3, water tank is equipped with automatic water inlet device.
BTR-500T, each heat load: 126000Kcal/h
is heated by a hot water furnace and a water tank. The hot water furnace is fully automatic for 24 hours (24 hours of work does not necessarily burn 24 hours).
2 hot water furnaces are connected in parallel, total heat load:
Input heat: 126000Kcal/h×2=252000Kcal/h
Output heat: 201600Kcal/h
Within an hour, heat Total heated water volume of the water furnace:
201600/(60-5) = 3600 liters 60℃
From the above calculation, it can be seen that the heating water volume of the hot water furnace is almost the same as Qh: the maximum hourly hot water consumption, slightly less than Qh, so the hot water tank is correspondingly made to a volume of 6M3 and an effective volume of 5M3 to achieve a 24-hour hot water supply.
General description:
1. The above water tank is an open water tank. After the water temperature is heated to the set temperature, the circulation between the hot water furnace and the water tank is stopped (the design institute also designed and installed an automatic control device) to achieve a 24-hour hot water supply.
2. This solution does not require manual management, and the hot water furnace body runs automatically.
Adjustment:
1) It can increase the water tank volume
2) It can increase the number of hot water furnaces and strive to have a backup furnace.
3) Ask customers for comments
Heating selection calculation:
Heating method:
Central heating: The city is divided into several heating networks according to the area, and the heating boilers are organized within the most economical and reasonable radius.
Slice heating: For more concentrated communities, smaller boilers can be built, which can reduce the laying of pipelines, but there will still be a 15% heat loss. With the development of the urban gas industry, gas has entered residents and can provide heating in segments in residential buildings. For example, a building can have a set of equipment.
household heating: Since gas has entered the household, you can choose a household hot water stove to heat according to the area of each household. Since there is no need for peripheral pipes, there will be no heat loss, and 100% of the heat is scattered in the house.
Heating calculation:
Known conditions:
What is the average temperature in the city where the user is located in January;
Which power does the user plan to use: gas type, oil, electricity, etc.;
The structure of the user's housing, insulation status. For example, an apartment building? Or a bungalow? villa? Single layer? Double glazing, etc.
Users want the indoor temperature.
Whether there is a cooling device in the original house, what kind of equipment is it, what kind of cooling device the user wants to choose, and what kind of equipment it is;
The use of the user's housing, the building area and the indoor height of the building. Where is the installation location of
and whether there are insulation measures.
Calculation:
(1) Selection of heating standards: Determine the calorific value of heat required per building area according to known conditions.
According to national standards, the normal room temperature is between 16-18℃.
The room temperature required for special requirements should be carefully converted and the calorific value should be increased accordingly.
The standard for building is to choose " calorific value ".
Note: The heat consumption per m2 in the south does not necessarily have to be less than that in the north, because:
All housing in the north are heated, and in winter, there is a hot end around, while in the south, you are the only one heating household, and the surrounding area is cold end around. At the same time, there is also a difference between apartment buildings and bungalows. Bungalows generally have a temperature difference, and are surrounded by cold ends, especially old bungalows, which increase the calorific value by 20%-30%.
The climate in the south is humid, and the air humidity increases the heating load.
(2) Determine the heating area:
Heating area is generally calculated based on the building area. Therefore, if the user tells the use area, it will increase by 25% to 40% during calculation. For example: the usable area is 80m2, the building area is: 80×1.4=112m2
(3) Heat supply:
Heating standard × standard building area = heating capacity (heat water furnace output power)
Example: an apartment in Beijing, with a usable area of 80m2, the heating standard is 60 kcal/m2, and the heating construction area = 80×1.4=112m2. Heat supply (heat output from the hot water furnace) = 112×60=6720 kcal/hour
(4) Heat input from the hot water furnace:
Hot water furnace efficiency has a great impact on use in heating and directly affects the heat supply. Therefore, it is necessary to be careful and consider the impact on thermal efficiency based on the user's gas source condition. If the heat value is lower than the designed gas calorific value, the gas input is insufficient and the output of the hot water furnace cannot reach the required capacity, and it is generally calculated based on a thermal efficiency of 75%. When the calorific value is higher than the designed gas calorific value, the thermal load capacity of the burner is insufficient and cannot achieve the required capacity, and will reduce the thermal efficiency and cause incomplete combustion.
is measured as 75% thermal efficiency, and the input heat should be 6720÷0.75=8960 kcal/hour.
(5) Selection:
Because the rated thermal load of EMG-20H is 9600 kcal/hour >8960 kcal/hour, EMG-20H can be used for heating for users with an area of 80M2, ensuring normal heating needs.
Heat dissipation method:
Heat dissipation principle:
Heating system In order to diffuse the heat of hot water to the air in the room, a reasonable heat dissipation form must be selected. The principle of heat dissipation is the same as the conduction method mentioned above. It uses the principles of convection heat transfer and heat conduction. The hot water forms a certain flow rate under the push of the circulating pump. The higher the flow rate, the higher the heat dissipation, and the heat is spread into the air through the radiator.
The form of radiator:
Heat sink:
Calculate the heat dissipation area according to the relative temperature drop of the heating temperature. Generally, the architectural design institute calculates according to relevant standards. The general water supply in my country is calculated at the standard of 95℃, return water temperature 70℃, and relative temperature drop of 25℃. Our hot water furnace water temperature is only 65℃ (or 76.6℃). According to the standard, the area of the heat sink must increase by 25-50% compared with 95℃ when heating, and the investment will increase by about 30%.
coil fan (heater):
uses fan coil forcibly exchange heat, with large heat exchange and large heating area, good effect
fan generally has water inlet at around 60℃, which is more suitable for our water hot furnace.
geothermal coil:
plastic aluminum composite pipe or crosslinked polyethylene pipe, can withstand water temperature of 90℃, lifespan can reach 40 years, with a pressure resistance of about 0.8Mpa, and can be bent in various shapes. Generally, the plate is under the floor and the hot water temperature is 50℃.
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-