Metal corrosion inhibitor composition for chillers and method for operating chillers

Abstract

To provide a metal corrosion inhibitor composition for chillers, capable of achieving a stable corrosion inhibition effect in a chiller water system; and a method for operating a chiller using the metal corrosion inhibitor composition for chillers.SOLUTION: A metal corrosion inhibitor composition for chillers contains water, an azole compound, and at least one of molybdenum acid and nitrous acid. The weight ratio of the azole compound in the metal corrosion inhibitor composition is 1 or more relative to the total weight ratio of at least one of the molybdenum acid (in terms of Mo) and the nitrous acid (in terms of NO2), while being 0.005 wt.% or more.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a metal corrosion inhibitor composition for a chiller and a method of operating a chiller using the metal corrosion inhibitor composition for a chiller. [Background technology]

[0002] A chiller system (cooling water circulation system), sometimes simply called a chiller, is a device that circulates water or a low-temperature heat medium adjusted to a specified temperature to cool, heat, or regulate the temperature of a target object such as a sample or device. Since most chillers are intended for cooling purposes, the circulating chiller water is sometimes called circulating water, circulating cooling water, or cooling water.

[0003] In various facilities and factories, cooling water, hot and cold water, and chiller water are widely used for cooling and heating equipment. In such water systems, the pipes and heat exchangers are often made of metals such as iron. How to prevent corrosion of such metal pipes and heat exchangers is one of the major issues facing cooling water systems, hot and cold water systems, and chiller water systems.

[0004] In general, hardness components such as calcium are present in the open-type cooling water that uses a cooling tower, and when part of the water evaporates in the cooling tower for cooling, the hardness components in the water become concentrated unless part of the cooling water is forcibly replaced. Since water that contains a large amount of hardness components generally does not corrode metals easily, corrosion can be suppressed by appropriately concentrating the cooling water and increasing the concentration of the hardness components. In such a system, it is possible to suppress damage to the cooling water system by adding a scale inhibitor such as a water-soluble polymer dispersant to suppress the formation of scale that clogs piping and interferes with heat transfer in heat exchangers.

[0005] Furthermore, when highly corrosive water, such as recovered water from process cleaning water in semiconductor factories, is used as make-up water for cooling water systems, the water generally has a low concentration of hardness components, and even if concentrated, the circulating cooling water has low hardness (for example, total hardness of 200 mgCaCO3 / L or less), making it highly corrosive to ferrous metals. When using such water as cooling water, the methods for inhibiting corrosion of ferrous metals are limited, and passive corrosion inhibition methods that form oxide films using chemicals such as molybdates are often used.

[0006] On the other hand, closed water systems such as closed cooling water, cold water for air conditioning, hot water, chiller water, etc. do not have cooling towers, the water is rarely concentrated, and generally has low hardness (for example, total hardness of 200 mgCaCO3 / liter or less), making it highly corrosive to ferrous metals. In addition, water and chemical replacement is extremely infrequent. Furthermore, operating conditions are often intermittent, and the specified flow rate cannot be constantly ensured. For these reasons, passive corrosion inhibition methods using chemicals such as molybdates and nitrites are often adopted.

[0007] Based on these technical theories, different chemicals are used depending on whether the water system is open or closed, or depending on the make-up water used, etc.

[0008] In addition, in closed water systems, copper-based and aluminum-based materials are often used as constituent materials for pipes, heat exchangers, water tanks, fins, etc. Corrosion inhibitors are often used for copper-based and aluminum-based materials, but because they are prone to corrosion when the pH becomes acidic or alkaline, methods are also used to create an environment that is less susceptible to corrosion by using pH adjusters.

[0009] Azole compounds, which are corrosion inhibitors used to inhibit the corrosion of copper-based materials, are generally effective at very low concentrations in the water being treated, so when an azole compound, which is a copper-based corrosion inhibitor, is used in combination with an iron-based corrosion inhibitor, the proportion of the iron-based corrosion inhibitor is overwhelmingly larger in terms of weight ratio (see, for example, Patent Document 1), and they are used in a weight ratio of, for example, 1:16. Examples of using an azole compound in a larger amount than an iron-based corrosion inhibitor do not exist substantially, except for antifreeze solutions whose main components are organic solvents, etc. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Application Publication No. 5-222555 Summary of the Invention [Problem to be solved by the invention]

[0011] In particular, in the case of chiller water circulated through a chiller, the chiller is generally a closed system with a cooling water inlet and a cooling water outlet connected to the object to be temperature-adjusted, and depending on the object to be temperature-adjusted, the amount of water held is small, and it is likely to be intermittent operation, such as stopping for one day or more per week, or stopping for three hours or more per day, and there are many cases where the composition ratio of iron-based metals is high and corrosion has already progressed within the system. As a result of the study by the present inventors, it was found that when the fluid temperature received by the chiller is 10°C or higher, when the chiller is in intermittent operation, or when the composition ratio of iron-based metals is high and corrosion has already progressed within the system, the azole compound is consumed particularly quickly compared to a general circulating water system. If the azole compound is consumed quickly, it needs to be replenished separately from the iron-based corrosion inhibitor, and if the timing of replenishing the azole compound is not judged, it may lead to corrosion of copper-based materials and cause problems such as secondary damage such as leakage to other heat transfer media due to leakage of water.

[0012] Therefore, there is a demand for a metal corrosion inhibitor composition for chillers that can provide a stable corrosion inhibition treatment effect in chiller water systems.

[0013] An object of the present invention is to provide a metal corrosion inhibitor composition for chillers that can provide a stable corrosion inhibition treatment effect in a chiller water system, and a method for operating a chiller that uses the metal corrosion inhibitor composition for chillers. [Means for solving the problem]

[0014] The present invention relates to a metal corrosion inhibitor composition for chillers, comprising water, an azole compound, and molybdenum. An acid, a fungus inhibitor, The weight ratio of the azole compound in the metal corrosion inhibitor composition is )of Percentage by weight 2.5 And 0.1~0.2 weight% Range Yes The weight ratio of the water in the metal corrosion inhibitor composition is 90% by weight or more, and the azole compound is at least one of benzotriazole, tolyltriazole, and aminotriazole. The present invention relates to a metal corrosion inhibitor composition for chillers.

[0016] In the metal corrosion inhibitor composition for chillers, the TOC in the metal corrosion inhibitor composition is preferably 10,000 mg / L or less.

[0018] The metal corrosion inhibitor composition for chillers preferably further contains at least one of a scale dispersant and a pH adjuster.

[0019] In the metal corrosion inhibitor composition for chillers, the pH of the metal corrosion inhibitor composition is preferably 5 or more.

[0020] The present invention is a method for operating a chiller using the metal corrosion inhibitor composition for chillers, in which the metal corrosion inhibitor composition for chillers is used as chiller water as it is.

[0021] In the chiller operation method, it is preferable that the temperature of a fluid received by the chiller from an object to be cooled is equal to or higher than 5°C and lower than 50°C.

[0022] In the method for operating a chiller, it is preferable to operate the chiller intermittently. Effect of the Invention

[0023] The present invention can provide a metal corrosion inhibitor composition for chillers that can provide a stable corrosion inhibition treatment effect in a chiller water system, and a method for operating a chiller that uses the metal corrosion inhibitor composition for chillers. [Brief description of the drawings]

[0024] [Figure 1] FIG. 1 is a schematic diagram showing an experimental setup in which a new test piece and a corroded test piece were placed face-to-face. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following describes an embodiment of the present invention. The embodiment is merely an example of implementing the present invention, and the present invention is not limited to the embodiment.

[0026] The metal corrosion inhibitor composition for chillers according to this embodiment contains water, an azole compound, and at least one of molybdic acid and nitrous acid, and the weight ratio of the azole compound in the metal corrosion inhibitor composition is 1 or more relative to the total weight ratio of at least one of molybdic acid (as Mo) and nitrous acid (as NO), and is 0.005% by weight or more.

[0027] The present inventors have significantly reconsidered the conventional common sense in composition design, for example, the ratio of an azole compound, which is a copper-based corrosion inhibitor, to an iron-based corrosion inhibitor in a weight ratio of 1:16 or 1:100, relative to the total weight ratio of at least one of molybdenum and nitrous acid, and have found that a stable corrosion inhibition treatment effect can be obtained in a chiller water system by combining the azole compound in an amount greater than or equal to the iron-based corrosion inhibitor and at 0.005% by weight or more.

[0028] By using the metal corrosion inhibitor composition for chillers according to this embodiment, a stable corrosion inhibition treatment effect can be obtained even in a closed chiller water system with a small amount of water held.

[0029] The metal corrosion inhibitor composition for chillers according to the present embodiment is mainly applied to closed chiller water systems. The chiller is not limited, and can be applied to, for example, various industrial machines, medical machines, physicochemical instruments, food machines, etc. The chiller may be equipped with, for example, a cooling section, and may be equipped with a water tank, a pump, etc. The chiller may be an air-cooled chiller or a water-cooled chiller. The amount of water held by the chiller is, for example, 100 L or less.

[0030] Examples of the azole compound that is a copper corrosion inhibitor include benzotriazole, tolyltriazole, and aminotriazole. The azole compound may be used alone or in combination of two or more.

[0031] Examples of the iron-based corrosion inhibitor include molybdic acid and nitrous acid. Molybdic acid is blended, for example, as a molybdate, and specific examples of the molybdate include molybdates such as orthomolybdate, paramolybdate, and metamolybdate. Specific examples of the salt in this case include sodium salt, potassium salt, and ammonium salt. Among these molybdates, sodium orthomolybdate is particularly preferred. When considering the weight of molybdic acid, it is preferable to convert it to Mo in terms of composition design because of ease of calculation. Nitrous acid is blended, for example, as a nitrite, and specific examples of the nitrite include sodium salt, potassium salt, and ammonium salt. When considering the weight of nitrous acid, it is preferable to convert it to NO2 in terms of composition design because of ease of calculation. The iron-based corrosion inhibitor may be used alone or in combination of two or more of these.

[0032] The water to be used can be tap water, pure water, ultrapure water, etc., but it is better to use pure water or ultrapure water. Here, pure water is water that has been treated so that both chloride ions and sulfate ions are less than 1 ppm. Ultrapure water is water with an electrical resistivity of 15 MΩ cm or more.

[0033] The metal corrosion inhibitor composition for chillers according to the present embodiment may contain a fungus inhibitor (also called a bactericide) in order to suppress the generation of slime and microbial corrosion. Examples of fungus inhibitors include organic sulfur-nitrogen compounds and organic bromine compounds, and specific examples thereof include 2-methyl-3-isothiazolone, 5-chloro-2-methyl-3-isothiazolone, 4,5-dichloro-2-n-octyl-3-isothiazolone, and 2-bromo-2-nitro-1,3-propanediol. The fungus inhibitor may be used alone or in combination of two or more of these.

[0034] The metal corrosion inhibitor composition for chillers according to the present embodiment may contain a scale inhibitor to inhibit the formation of scale. As the scale inhibitor, a polycarboxylic acid compound, a chelating agent, or the like is used. Specific examples of the polycarboxylic acid compound include polyacrylic acid, polymaleic acid, a copolymer of acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid, and sodium salts thereof. Specific examples of chelating agents include L-ascorbic acid, erythorbic acid and their sodium salts, ethylenediaminetetraacetic acid (EDTA), ethylenediamine-N,N'-disuccinic acid (EDDS), nitrilotriacetic acid (NTA), diethylenetriaminepentaacetic acid (DTPA), L-aspartic acid diacetic acid (ASDA), L-glutamic acid diacetic acid (GLDA), hydroxyethylethylenediaminetriacetic acid (HEDTA), methylglycine diacetic acid (MGDA), glycol ether diaminetetraacetic acid (GEDTA), triethylenetetraminehexaacetic acid (TTHA), hydroxyethyliminodiacetic acid (HIDA), and their sodium salts, potassium salts, hydrates, etc. The scale inhibitors may be used alone or in combination of two or more.

[0035] In a closed water environment such as chiller water, water is hardly exchanged, so when metal corrosion occurs in the system, the pH may rise due to hydroxide ions generated by the progress of the cathodic reaction, and a problem of promoting copper-based metals may occur secondarily. Therefore, it is desirable to blend a pH adjuster into the metal corrosion inhibitor composition for chillers. Examples of pH adjusters include sodium carbonate, potassium carbonate, sodium bicarbonate, sodium phosphate, disodium hydrogen phosphate, potassium phosphate, trisodium citrate, sodium gluconate, etc., and carbonates and bicarbonates such as sodium carbonate, potassium carbonate, and sodium bicarbonate are preferable because they are less likely to become scale components or TOC sources. The pH adjuster may be used alone or in combination of two or more of these.

[0036] The pH of the metal corrosion inhibitor composition for a chiller is preferably not less than 4, and more preferably not less than 5. The upper limit of the pH of the metal corrosion inhibitor composition for a chiller is, for example, not more than 11.

[0037] In the metal corrosion inhibitor composition for chillers according to the present embodiment, the azole compound is preferably blended in a weight ratio of at least one of molybdic acid and nitrous acid, which are iron-based corrosion inhibitors (i.e., the weight ratio of the azole compound is 1 or more relative to the total weight ratio of at least one of molybdic acid and nitrous acid), and the weight ratio of the azole compound: at least one of molybdenum and nitrous acid is preferably in the range of 1:1 to 100:1, more preferably in the range of 1:1 to 10:1. In cases where the proportion of copper-based metals in the composition of the treated metal is low, the weight ratio of the azole compound: at least one of molybdic acid and nitrous acid may be preferably in the range of about 1:10 to 10:1. Here, the weight of molybdic acid is the weight as Mo, and the weight of nitrous acid is the weight as NO2.

[0038] The weight ratio of the azole compound in the metal corrosion inhibitor composition for chillers according to this embodiment is 0.005% by weight or more, preferably in the range of 0.005 to 1.0% by weight, and more preferably in the range of 0.005 to 0.2% by weight.

[0039] The metal corrosion inhibitor composition for chillers according to the present embodiment is a composition that is not composed of an organic solvent. "Not composed of an organic solvent" is defined as a composition that has a TOC of 10,000 mg / L or less, taking into consideration the increase in TOC caused by blending an azole compound, an organic fungus inhibitor, etc. in an appropriate amount. The TOC is preferably 3,000 mg / L or less. The metal corrosion inhibitor composition for chillers according to the present embodiment is preferably a composition in which the TOC component is composed only of an azole compound and an organic fungus inhibitor.

[0040] The weight ratio of water in the metal corrosion inhibitor composition for chillers according to the present embodiment is, for example, 90% by weight or more, preferably 99% by weight or more, and more preferably 99.5% by weight or more. In general, in the case of an antifreeze concentrate, the main components ethylene glycol or propylene glycol are contained in an amount of about 70 to 80% by weight, and the water content is about 20 to 30% by weight, and the concentrate is used as is or diluted several times with water. Therefore, it should be considered as having completely different properties from the metal corrosion inhibitor composition for chillers according to the present embodiment, which is composed of 99% by weight or more of water.

[0041] The metal corrosion inhibitor composition for chillers according to the present embodiment may be used as chiller water as it is, instead of being used by adding a concentrated agent to a water system as in the case of a typical composition for cooling water.

[0042] <How to operate the chiller> The chiller operating method according to the present embodiment is an operating method using the above-mentioned metal corrosion inhibitor composition for chillers. For example, the above-mentioned metal corrosion inhibitor composition for chillers may be used as circulating water (also called circulating cooling water or cooling water) for the chiller to operate the chiller.

[0043] The metal corrosion inhibitor composition for chillers can be suitably used as circulating water for chillers when the fluid temperature received by the chiller from an object to be temperature-adjusted is, for example, in the range of 5° C. or more and less than 50° C., and preferably in the range of 10° C. or more and less than 30° C. By using the metal corrosion inhibitor composition for chillers, a stable corrosion inhibition treatment effect can be obtained even if the fluid temperature received by the chiller from an object to be temperature-adjusted is in the range of 5° C. or more and less than 50° C.

[0044] When the chiller is operated intermittently, for example, at an operating rate of 90% or less, preferably at an operating rate of 10% to 90%, the above-mentioned metal corrosion inhibitor composition for chillers can be suitably used as circulating water for the chiller. By using the above-mentioned metal corrosion inhibitor composition for chillers, a stable corrosion inhibition treatment effect can be obtained even when the chiller is operated intermittently.

[0045] Note that an "operational rate of 90% or less" means that the chiller is stopped for one day or more per week, or for three hours or more per day; in other words, the operating time over a seven-day period is intermittent operation with an operating rate of 90% or less. EXAMPLES

[0046] EXAMPLES The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0047] <Example> 7, Reference example 1~ 6,8, 9. Comparative Examples 1 to 3 Working Example , reference example In the comparative example, a rotary corrosion test was carried out by placing a total of four pieces of test pieces, namely, a brand new mild steel test piece, a copper test piece, and a mild steel test piece and a copper test piece that had been corroded separately, in the test solution described below that had been prepared in advance.

[0048] The corroded mild steel test pieces were prepared by immersing new mild steel test pieces in Sagamihara city water and corroding them for 7 days at 35°C with agitation at 200 rpm. The corroded copper test pieces were prepared by immersing new copper test pieces in an ammonia-containing solution prepared by adding 30% ammonia water to pure water to adjust the ammonium ion concentration to 60 ppm, and corroding them for 7 days at 35°C with agitation at 200 rpm.

[0049] A total of four test pieces were immersed in a beaker filled with 1 L of test liquid using a special cross-shaped test piece mounting resin that can simultaneously mount a total of four test pieces, such as a new mild steel test piece facing a corroded mild steel test piece, and a new copper test piece facing a corroded copper test piece, and a rotary corrosion test was performed. Figure 1 shows a schematic diagram of the experimental apparatus in which the new test piece and the corroded test piece are placed facing each other. In the experimental apparatus in Figure 1, a new test piece 12 and a corroded test piece 14 are immersed in the test liquid 16 in a beaker 10 facing each other using a test piece mounting resin 18.

[0050] In the rotary corrosion test, the impeller (resin for mounting the test specimen) with the test specimen attached was rotated at 150 rpm for three days, then the stirring was stopped for two days and the specimen was left stationary with a zero flow rate, after which the impeller with the test specimen attached was rotated again at 150 rpm for two days. After seven days, the test specimen was removed, and the originally brand new test specimen was derusted and weighed. The corrosion rates of mild steel and copper were measured by the mass subtraction method in accordance with the Industrial Water Corrosion Test Method (JIS-K0100) based on the difference from the test specimen weight measured before the start of the test.

[0051] [Test conditions] Test liquid: Pure water containing the corrosion inhibitor components (benzotriazole and sodium molybdate or sodium nitrite) and fungus inhibitor ( reference Example 4 and Example 7) were mixed at a predetermined concentration, 500 mg / L of sodium bicarbonate was added as a pH adjuster, and the test pH was adjusted to 7.2±0.2. 1 L of the mixture was placed in a 1 L beaker for testing. reference The fungus inhibitors used in Examples 4 and 7 were 2-bromo-2-nitro-1,3-propanediol at a concentration of 100 mg / L and Caisson WT (the trade name of an isothiazolinone fungus inhibitor) at a concentration of 200 mg / L. Water temperature: 30℃ Stirring speed: 150 rpm Test piece: Mild steel SS-400 (10 x 30 x 50 mm, #400) Copper C1220P (10×30×50mm, #400) Test period: 7 days (3 days of continuous operation, 2 days of stoppage, 2 days of continuous operation (assuming 2 days of stoppage in a week))

[0052] The test results are shown in Tables 1 and 2. In Tables 1 and 2, "Mo" stands for sodium molybdate (concentration is Mo), "NO2" stands for sodium nitrite (concentration is NO2), and "AZ" stands for benzotriazole ( reference (Example 2: Tolyltriazole) "MDD" is the unit of corrosion rate, mg / dm 2 Represents day.

[0053] The TOC of the test water was measured by a combustion catalytic oxidation method using a total organic carbon meter (Shimadzu Corporation, model: TOC-L-CPN), and was approximately 1,400 mg / L for pure water mixed with 800 mg / L of sodium molybdate, 2,000 mg / L of benzotriazole, 100 mg / L of 2-bromo-2-nitro-1,3-propanediol, 200 mg / L of Caisson WT, and 500 mg / L of sodium bicarbonate (Example 7).

[0054] The molybdenum concentration was measured using the HACH "DR-3900." The nitrite concentration was measured using the DIONEX "Integrion" ion chromatography. The azole compound concentration was measured using the HACH "DR-3900."

[0055] After the test, the number of general bacteria in the water in the beaker was measured. A San-Ai Biochecker TTC made by San-Ai Oil Co., Ltd. was placed in the water for 5 seconds, removed, and then cultured in a thermostatic chamber set at 30°C for 48 hours. The colony pattern appearing on the surface of the removed Biochecker medium was compared with the sample and calculated as the number of colonies in the logarithmic order of 10.

[0056] [Pass / Fail criteria] In this test, the pass / fail criteria were set as follows: Corrosion rate of mild steel (MDD): 10 or less is considered a pass. Copper corrosion rate (MDD): 0.5 or less is considered a pass. Residual concentration of iron-based corrosion inhibitors (molybdic acid (as Mo), nitrous acid (as NO2)): 70% or more is considered a pass. Residual concentration of copper-based corrosion inhibitor (azole compound): 90% or more is considered a pass.

[0057] [Table 1]

[0058] [Table 2]

[0059] As in the comparative example, it was found that when the weight ratio of the azole compound is less than 1 relative to the total weight ratio of at least one of molybdic acid (as Mo) and nitrous acid (as NO2), the concentration of the azole compound and at least one of molybdic acid and nitrous acid in the treated water drops drastically. The reason for this is unclear, but it is presumed that the high concentration of the oxide film type agent (at least one of molybdic acid and nitrous acid), which is an iron-based corrosion inhibitor, increases the potential of the iron surface and relatively decreases the potential of the copper surface, creating an environment in which the copper-based material is prone to corrosion, and in such an environment, if the azole compound, which is a copper-based corrosion inhibitor, is not supplied at a predetermined concentration or more, the copper-based material corrodes, and the azole compound, molybdic acid, etc. are consumed in the form of being taken up in the corrosion product, creating an environment in which the iron-based material also corrodes secondarily. On the other hand, it is presumed that such a phenomenon hardly occurs and a stable corrosion inhibition treatment effect can be obtained under conditions in which the weight ratio of the azole compound is 1 or more relative to the total weight ratio of at least one of molybdic acid (as Mo) and nitrous acid (as NO2) and is 0.005 wt% or more.

[0060] Also, reference Example 4, Working Example From the results of 7, it was confirmed that the incorporation of a fungus inhibitor could provide a good bactericidal effect of less than 10 to the power of 3.

[0061] As described above, the metal corrosion inhibitor composition for chillers of the examples provided a stable corrosion inhibition treatment effect in the chiller water system. [Explanation of symbols]

[0062] 10 beaker, 12 new test specimen, 14 corroded test specimen, 16 test liquid, 18 resin for mounting test specimen.

Claims

1. A metal corrosion inhibitor composition for a chiller, comprising: Contains water, an azole compound, molybdic acid, and a fungus inhibitor; the weight ratio of the azole compound in the metal corrosion inhibitor composition is 2.5 or more and in the range of 0.1 to 0.2% by weight based on the weight ratio of the molybdic acid (as Mo); The weight ratio of the water in the metal corrosion inhibitor composition is 90% by weight or more, The metal corrosion inhibitor composition for chillers, wherein the azole compound is at least one of benzotriazole, tolyltriazole, and aminotriazole.

2. The metal corrosion inhibitor composition for chillers according to claim 1, A metal corrosion inhibitor composition for chillers, characterized in that the TOC in the metal corrosion inhibitor composition is 10,000 mg / L or less.

3. The metal corrosion inhibitor composition for chillers according to claim 1 or 2, The metal corrosion inhibitor composition for chillers further comprises at least one of a scale dispersant and a pH adjuster.

4. The metal corrosion inhibitor composition for chillers according to any one of claims 1 to 3, The metal corrosion inhibitor composition for chillers, wherein the pH of the metal corrosion inhibitor composition is 5 or more.

5. A method for operating a chiller using the metal corrosion inhibitor composition for chillers according to any one of claims 1 to 4, A method for operating a chiller, comprising using the above-mentioned metal corrosion inhibitor composition for chillers as chiller water as it is.

6. A method for operating a chiller according to claim 5, comprising: A method for operating a chiller, wherein the temperature of a fluid received by the chiller from an object to be temperature-adjusted is equal to or higher than 5°C and lower than 50°C.

7. A method for operating a chiller according to claim 5 or 6, comprising: A method for operating a chiller, comprising intermittently operating the chiller.

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